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@ -1,6 +1,6 @@
<h3>About Flask</h3>
<p>
Flask is a micro webdevelopment framework for Python. You are currently
Flask is a micro web development framework for Python. You are currently
looking at the documentation of the development version.
</p>
<h3>Other Formats</h3>
@ -16,7 +16,7 @@
<h3>Useful Links</h3>
<ul>
<li><a href="http://flask.pocoo.org/">The Flask Website</a></li>
<li><a href="http://pypi.python.org/pypi/Flask">Flask @ PyPI</a></li>
<li><a href="http://github.com/pallets/flask">Flask @ GitHub</a></li>
<li><a href="http://github.com/pallets/flask/issues">Issue Tracker</a></li>
<li><a href="https://pypi.python.org/pypi/Flask">Flask @ PyPI</a></li>
<li><a href="https://github.com/pallets/flask">Flask @ GitHub</a></li>
<li><a href="https://github.com/pallets/flask/issues">Issue Tracker</a></li>
</ul>

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@ -29,62 +29,13 @@ Incoming Request Data
---------------------
.. autoclass:: Request
:members: is_json, get_json
.. attribute:: form
A :class:`~werkzeug.datastructures.MultiDict` with the parsed form data from ``POST``
or ``PUT`` requests. Please keep in mind that file uploads will not
end up here, but instead in the :attr:`files` attribute.
.. attribute:: args
A :class:`~werkzeug.datastructures.MultiDict` with the parsed contents of the query
string. (The part in the URL after the question mark).
.. attribute:: values
A :class:`~werkzeug.datastructures.CombinedMultiDict` with the contents of both
:attr:`form` and :attr:`args`.
.. attribute:: cookies
A :class:`dict` with the contents of all cookies transmitted with
the request.
.. attribute:: stream
If the incoming form data was not encoded with a known mimetype
the data is stored unmodified in this stream for consumption. Most
of the time it is a better idea to use :attr:`data` which will give
you that data as a string. The stream only returns the data once.
.. attribute:: headers
The incoming request headers as a dictionary like object.
.. attribute:: data
Contains the incoming request data as string in case it came with
a mimetype Flask does not handle.
.. attribute:: files
A :class:`~werkzeug.datastructures.MultiDict` with files uploaded as part of a
``POST`` or ``PUT`` request. Each file is stored as
:class:`~werkzeug.datastructures.FileStorage` object. It basically behaves like a
standard file object you know from Python, with the difference that
it also has a :meth:`~werkzeug.datastructures.FileStorage.save` function that can
store the file on the filesystem.
:members:
:inherited-members:
.. attribute:: environ
The underlying WSGI environment.
.. attribute:: method
The current request method (``POST``, ``GET`` etc.)
.. attribute:: path
.. attribute:: full_path
.. attribute:: script_root
@ -114,15 +65,8 @@ Incoming Request Data
`url_root` ``u'http://www.example.com/myapplication/'``
============= ======================================================
.. attribute:: is_xhr
``True`` if the request was triggered via a JavaScript
`XMLHttpRequest`. This only works with libraries that support the
``X-Requested-With`` header and set it to `XMLHttpRequest`.
Libraries that do that are prototype, jQuery and Mochikit and
probably some more.
.. class:: request
.. attribute:: request
To access incoming request data, you can use the global `request`
object. Flask parses incoming request data for you and gives you
@ -227,18 +171,6 @@ implementation that Flask is using.
.. autoclass:: SessionMixin
:members:
.. autodata:: session_json_serializer
This object provides dumping and loading methods similar to simplejson
but it also tags certain builtin Python objects that commonly appear in
sessions. Currently the following extended values are supported in
the JSON it dumps:
- :class:`~markupsafe.Markup` objects
- :class:`~uuid.UUID` objects
- :class:`~datetime.datetime` objects
- :class:`tuple`\s
.. admonition:: Notice
The ``PERMANENT_SESSION_LIFETIME`` config key can also be an integer
@ -316,13 +248,7 @@ Useful Functions and Classes
.. autofunction:: url_for
.. function:: abort(code)
Raises an :exc:`~werkzeug.exceptions.HTTPException` for the given
status code. For example to abort request handling with a page not
found exception, you would call ``abort(404)``.
:param code: the HTTP error code.
.. autofunction:: abort
.. autofunction:: redirect
@ -416,6 +342,8 @@ you are using Flask 0.10 which implies that:
.. autoclass:: JSONDecoder
:members:
.. automodule:: flask.json.tag
Template Rendering
------------------

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@ -5,31 +5,37 @@ The Application Context
.. versionadded:: 0.9
One of the design ideas behind Flask is that there are two different
“states” in which code is executed. The application setup state in which
the application implicitly is on the module level. It starts when the
:class:`Flask` object is instantiated, and it implicitly ends when the
first request comes in. While the application is in this state a few
assumptions are true:
One of the design ideas behind Flask is that there are at least two
different “states” in which code is executed:
- the programmer can modify the application object safely.
- no request handling happened so far
- you have to have a reference to the application object in order to
modify it, there is no magic proxy that can give you a reference to
the application object you're currently creating or modifying.
1. The application setup state, in which the application implicitly is
on the module level.
In contrast, during request handling, a couple of other rules exist:
This state starts when the :class:`Flask` object is instantiated, and
it implicitly ends when the first request comes in. While the
application is in this state, a few assumptions are true:
- while a request is active, the context local objects
(:data:`flask.request` and others) point to the current request.
- any code can get hold of these objects at any time.
- the programmer can modify the application object safely.
- no request handling happened so far
- you have to have a reference to the application object in order to
modify it, there is no magic proxy that can give you a reference to
the application object you're currently creating or modifying.
There is a third state which is sitting in between a little bit.
Sometimes you are dealing with an application in a way that is similar to
how you interact with applications during request handling; just that there
is no request active. Consider, for instance, that you're sitting in an
interactive Python shell and interacting with the application, or a
command line application.
2. In contrast, in the request handling state, a couple of other rules
exist:
- while a request is active, the context local objects
(:data:`flask.request` and others) point to the current request.
- any code can get hold of these objects at any time.
3. There is also a third state somewhere in between 'module-level' and
'request-handling':
Sometimes you are dealing with an application in a way that is similar to
how you interact with applications during request handling, but without
there being an active request. Consider, for instance, that you're
sitting in an interactive Python shell and interacting with the
application, or a command line application.
The application context is what powers the :data:`~flask.current_app`
context local.

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@ -12,7 +12,7 @@ Flask started in part to demonstrate how to build your own framework on top of
existing well-used tools Werkzeug (WSGI) and Jinja (templating), and as it
developed, it became useful to a wide audience. As you grow your codebase,
don't just use Flask -- understand it. Read the source. Flask's code is
written to be read; it's documentation is published so you can use its internal
written to be read; its documentation is published so you can use its internal
APIs. Flask sticks to documented APIs in upstream libraries, and documents its
internal utilities so that you can find the hook points needed for your
project.

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@ -177,11 +177,11 @@ the `template_folder` parameter to the :class:`Blueprint` constructor::
admin = Blueprint('admin', __name__, template_folder='templates')
For static files, the path can be absolute or relative to the blueprint
resource folder.
resource folder.
The template folder is added to the search path of templates but with a lower
priority than the actual application's template folder. That way you can
easily override templates that a blueprint provides in the actual application.
The template folder is added to the search path of templates but with a lower
priority than the actual application's template folder. That way you can
easily override templates that a blueprint provides in the actual application.
This also means that if you don't want a blueprint template to be accidentally
overridden, make sure that no other blueprint or actual application template
has the same relative path. When multiple blueprints provide the same relative
@ -194,7 +194,7 @@ want to render the template ``'admin/index.html'`` and you have provided
this: :file:`yourapplication/admin/templates/admin/index.html`. The reason
for the extra ``admin`` folder is to avoid getting our template overridden
by a template named ``index.html`` in the actual application template
folder.
folder.
To further reiterate this: if you have a blueprint named ``admin`` and you
want to render a template called :file:`index.html` which is specific to this
@ -245,4 +245,22 @@ Here is an example for a "404 Page Not Found" exception::
def page_not_found(e):
return render_template('pages/404.html')
Most errorhandlers will simply work as expected; however, there is a caveat
concerning handlers for 404 and 405 exceptions. These errorhandlers are only
invoked from an appropriate ``raise`` statement or a call to ``abort`` in another
of the blueprint's view functions; they are not invoked by, e.g., an invalid URL
access. This is because the blueprint does not "own" a certain URL space, so
the application instance has no way of knowing which blueprint errorhandler it
should run if given an invalid URL. If you would like to execute different
handling strategies for these errors based on URL prefixes, they may be defined
at the application level using the ``request`` proxy object::
@app.errorhandler(404)
@app.errorhandler(405)
def _handle_api_error(ex):
if request.path.startswith('/api/'):
return jsonify_error(ex)
else:
return ex
More information on error handling see :ref:`errorpages`.

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@ -56,14 +56,24 @@ If you are constantly working with a virtualenv you can also put the
bottom of the file. That way every time you activate your virtualenv you
automatically also activate the correct application name.
Edit the activate script for the shell you use. For example:
Unix Bash: ``venv/bin/activate``::
FLASK_APP=hello
export FLASK_APP
Windows CMD.exe: ``venv\Scripts\activate.bat``::
set "FLASK_APP=hello"
:END
Debug Flag
----------
The :command:`flask` script can also be instructed to enable the debug
mode of the application automatically by exporting ``FLASK_DEBUG``. If
set to ``1`` debug is enabled or ``0`` disables it.
Or with a filename::
set to ``1`` debug is enabled or ``0`` disables it::
export FLASK_DEBUG=1
@ -141,8 +151,8 @@ This could be a file named :file:`autoapp.py` with these contents::
from yourapplication import create_app
app = create_app(os.environ['YOURAPPLICATION_CONFIG'])
Once this has happened you can make the flask command automatically pick
it up::
Once this has happened you can make the :command:`flask` command automatically
pick it up::
export YOURAPPLICATION_CONFIG=/path/to/config.cfg
export FLASK_APP=/path/to/autoapp.py
@ -248,3 +258,46 @@ Inside :file:`mypackage/commands.py` you can then export a Click object::
Once that package is installed in the same virtualenv as Flask itself you
can run ``flask my-command`` to invoke your command. This is useful to
provide extra functionality that Flask itself cannot ship.
PyCharm Integration
-------------------
The new Flask CLI features aren’t yet fully integrated into the PyCharm IDE,
so we have to do a few tweaks to get them working smoothly.
In your PyCharm application, with your project open, click on *Run*
from the menu bar and go to *Edit Configurations*. You’ll be greeted by a
screen similar to this:
.. image:: _static/pycharm-runconfig.png
:align: center
:class: screenshot
:alt: screenshot of pycharm's run configuration settings
There’s quite a few options to change, but don’t worry— once we’ve done it
for one command, we can easily copy the entire configuration and make a
single tweak to give us access to other flask cli commands, including
any custom ones you may implement yourself.
For the *Script* input (**A**), we want to navigate to the virtual environment
we’re using for our project and within that folder we want to pick the ``flask``
file which will reside in the ``bin`` folder, or in the ``Scripts`` folder if
you're on Windows.
The *Script Parameter* field (**B**) is set to the cli command you wish to
execute, in this example we use ``run`` which will run our development server.
We need to add an environment variable (**C**) to identify our application.
Click on the browse button and add an entry with ``FLASK_APP`` on the
left and the name of the python file, or package on the right
(``app.py`` for example).
Next we need to set the working directory (**D**) to be the same folder where
our application file or package resides.
Finally, untick the *PYTHONPATH* options (**E**) and give the configuration a
good descriptive name, such as “Run Flask Server” and click *Apply*.
Now that we have on run configuration which implements ``flask run`` from within
PyCharm, we can simply copy that configuration and alter the script argument
to run a different cli command, e.g. ``flask shell``.

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@ -11,15 +11,17 @@
# All configuration values have a default; values that are commented out
# serve to show the default.
from __future__ import print_function
from datetime import datetime
import os
import sys
import pkg_resources
import time
import datetime
BUILD_DATE = datetime.datetime.utcfromtimestamp(int(os.environ.get('SOURCE_DATE_EPOCH', time.time())))
# If extensions (or modules to document with autodoc) are in another directory,
# add these directories to sys.path here. If the directory is relative to the
# documentation root, use os.path.abspath to make it absolute, like shown here.
sys.path.append(os.path.join(os.path.dirname(__file__), '_themes'))
sys.path.append(os.path.dirname(__file__))
# -- General configuration -----------------------------------------------------
@ -35,6 +37,14 @@ extensions = [
'flaskdocext'
]
try:
__import__('sphinxcontrib.log_cabinet')
except ImportError:
print('sphinxcontrib-log-cabinet is not installed.')
print('Changelog directives will not be re-organized.')
else:
extensions.append('sphinxcontrib.log_cabinet')
# Add any paths that contain templates here, relative to this directory.
templates_path = ['_templates']
@ -49,7 +59,7 @@ master_doc = 'index'
# General information about the project.
project = u'Flask'
copyright = u'2010 - {0}, Armin Ronacher'.format(datetime.utcnow().year)
copyright = u'2010 - {0}, Armin Ronacher'.format(BUILD_DATE.year)
# The version info for the project you're documenting, acts as replacement for
# |version| and |release|, also used in various other places throughout the
@ -110,7 +120,7 @@ exclude_patterns = ['_build']
# html_theme_options = {}
# Add any paths that contain custom themes here, relative to this directory.
html_theme_path = ['_themes']
# html_theme_path = ['_themes']
# The name for this set of Sphinx documents. If None, it defaults to
# "<project> v<release> documentation".
@ -231,7 +241,7 @@ latex_additional_files = ['flaskstyle.sty', 'logo.pdf']
# The scheme of the identifier. Typical schemes are ISBN or URL.
#epub_scheme = ''
# The unique identifier of the text. This can be a ISBN number
# The unique identifier of the text. This can be an ISBN number
# or the project homepage.
#epub_identifier = ''
@ -257,26 +267,14 @@ intersphinx_mapping = {
'werkzeug': ('http://werkzeug.pocoo.org/docs/', None),
'click': ('http://click.pocoo.org/', None),
'jinja': ('http://jinja.pocoo.org/docs/', None),
'sqlalchemy': ('http://docs.sqlalchemy.org/en/latest/', None),
'sqlalchemy': ('https://docs.sqlalchemy.org/en/latest/', None),
'wtforms': ('https://wtforms.readthedocs.io/en/latest/', None),
'blinker': ('https://pythonhosted.org/blinker/', None)
}
try:
__import__('flask_theme_support')
pygments_style = 'flask_theme_support.FlaskyStyle'
html_theme = 'flask'
html_theme_options = {
'touch_icon': 'touch-icon.png'
}
except ImportError:
print('-' * 74)
print('Warning: Flask themes unavailable. Building with default theme')
print('If you want the Flask themes, run this command and build again:')
print()
print(' git submodule update --init')
print('-' * 74)
html_theme_options = {
'touch_icon': 'touch-icon.png'
}
# unwrap decorators
def unwrap_decorators():

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@ -3,8 +3,6 @@
Configuration Handling
======================
.. versionadded:: 0.3
Applications need some kind of configuration. There are different settings
you might want to change depending on the application environment like
toggling the debug mode, setting the secret key, and other such
@ -44,178 +42,263 @@ method::
SECRET_KEY='...'
)
.. admonition:: Debug Mode with the ``flask`` Script
If you use the :command:`flask` script to start a local development
server, to enable the debug mode, you need to export the ``FLASK_DEBUG``
environment variable before running the server::
$ export FLASK_DEBUG=1
$ flask run
(On Windows you need to use ``set`` instead of ``export``).
``app.debug`` and ``app.config['DEBUG']`` are not compatible with
  the :command:`flask` script. They only worked when using ``Flask.run()``
method.
Builtin Configuration Values
----------------------------
The following configuration values are used internally by Flask:
.. tabularcolumns:: |p{6.5cm}|p{8.5cm}|
.. py:data:: DEBUG
================================= =========================================
``DEBUG`` enable/disable debug mode
``TESTING`` enable/disable testing mode
``PROPAGATE_EXCEPTIONS`` explicitly enable or disable the
propagation of exceptions. If not set or
explicitly set to ``None`` this is
implicitly true if either ``TESTING`` or
``DEBUG`` is true.
``PRESERVE_CONTEXT_ON_EXCEPTION`` By default if the application is in
debug mode the request context is not
popped on exceptions to enable debuggers
to introspect the data. This can be
disabled by this key. You can also use
this setting to force-enable it for non
debug execution which might be useful to
debug production applications (but also
very risky).
``SECRET_KEY`` the secret key
``SESSION_COOKIE_NAME`` the name of the session cookie
``SESSION_COOKIE_DOMAIN`` the domain for the session cookie. If
this is not set, the cookie will be
valid for all subdomains of
``SERVER_NAME``.
``SESSION_COOKIE_PATH`` the path for the session cookie. If
this is not set the cookie will be valid
for all of ``APPLICATION_ROOT`` or if
that is not set for ``'/'``.
``SESSION_COOKIE_HTTPONLY`` controls if the cookie should be set
with the httponly flag. Defaults to
``True``.
``SESSION_COOKIE_SECURE`` controls if the cookie should be set
with the secure flag. Defaults to
``False``.
``PERMANENT_SESSION_LIFETIME`` the lifetime of a permanent session as
:class:`datetime.timedelta` object.
Starting with Flask 0.8 this can also be
an integer representing seconds.
``SESSION_REFRESH_EACH_REQUEST`` this flag controls how permanent
sessions are refreshed. If set to ``True``
(which is the default) then the cookie
is refreshed each request which
automatically bumps the lifetime. If
set to ``False`` a `set-cookie` header is
only sent if the session is modified.
Non permanent sessions are not affected
by this.
``USE_X_SENDFILE`` enable/disable x-sendfile
``LOGGER_NAME`` the name of the logger
``LOGGER_HANDLER_POLICY`` the policy of the default logging
handler. The default is ``'always'``
which means that the default logging
handler is always active. ``'debug'``
will only activate logging in debug
mode, ``'production'`` will only log in
production and ``'never'`` disables it
entirely.
``SERVER_NAME`` the name and port number of the server.
Required for subdomain support (e.g.:
``'myapp.dev:5000'``) Note that
localhost does not support subdomains so
setting this to “localhost” does not
help. Setting a ``SERVER_NAME`` also
by default enables URL generation
without a request context but with an
application context.
``APPLICATION_ROOT`` If the application does not occupy
a whole domain or subdomain this can
be set to the path where the application
is configured to live. This is for
session cookie as path value. If
domains are used, this should be
``None``.
``MAX_CONTENT_LENGTH`` If set to a value in bytes, Flask will
reject incoming requests with a
content length greater than this by
returning a 413 status code.
``SEND_FILE_MAX_AGE_DEFAULT`` Default cache control max age to use with
:meth:`~flask.Flask.send_static_file` (the
default static file handler) and
:func:`~flask.send_file`, as
:class:`datetime.timedelta` or as seconds.
Override this value on a per-file
basis using the
:meth:`~flask.Flask.get_send_file_max_age`
hook on :class:`~flask.Flask` or
:class:`~flask.Blueprint`,
respectively. Defaults to 43200 (12 hours).
``TRAP_HTTP_EXCEPTIONS`` If this is set to ``True`` Flask will
not execute the error handlers of HTTP
exceptions but instead treat the
exception like any other and bubble it
through the exception stack. This is
helpful for hairy debugging situations
where you have to find out where an HTTP
exception is coming from.
``TRAP_BAD_REQUEST_ERRORS`` Werkzeug's internal data structures that
deal with request specific data will
raise special key errors that are also
bad request exceptions. Likewise many
operations can implicitly fail with a
BadRequest exception for consistency.
Since it's nice for debugging to know
why exactly it failed this flag can be
used to debug those situations. If this
config is set to ``True`` you will get
a regular traceback instead.
``PREFERRED_URL_SCHEME`` The URL scheme that should be used for
URL generation if no URL scheme is
available. This defaults to ``http``.
``JSON_AS_ASCII`` By default Flask serialize object to
ascii-encoded JSON. If this is set to
``False`` Flask will not encode to ASCII
and output strings as-is and return
unicode strings. ``jsonify`` will
automatically encode it in ``utf-8``
then for transport for instance.
``JSON_SORT_KEYS`` By default Flask will serialize JSON
objects in a way that the keys are
ordered. This is done in order to
ensure that independent of the hash seed
of the dictionary the return value will
be consistent to not trash external HTTP
caches. You can override the default
behavior by changing this variable.
This is not recommended but might give
you a performance improvement on the
cost of cachability.
``JSONIFY_PRETTYPRINT_REGULAR`` If this is set to ``True`` (the default)
jsonify responses will be pretty printed
if they are not requested by an
XMLHttpRequest object (controlled by
the ``X-Requested-With`` header)
``JSONIFY_MIMETYPE`` MIME type used for jsonify responses.
``TEMPLATES_AUTO_RELOAD`` Whether to check for modifications of
the template source and reload it
automatically. By default the value is
``None`` which means that Flask checks
original file only in debug mode.
``EXPLAIN_TEMPLATE_LOADING`` If this is enabled then every attempt to
load a template will write an info
message to the logger explaining the
attempts to locate the template. This
can be useful to figure out why
templates cannot be found or wrong
templates appear to be loaded.
================================= =========================================
Enable debug mode. When using the development server with ``flask run`` or
``app.run``, an interactive debugger will be shown for unhanlded
exceptions, and the server will be reloaded when code changes.
.. admonition:: More on ``SERVER_NAME``
**Do not enable debug mode in production.**
The ``SERVER_NAME`` key is used for the subdomain support. Because
Flask cannot guess the subdomain part without the knowledge of the
actual server name, this is required if you want to work with
subdomains. This is also used for the session cookie.
Default: ``False``
Please keep in mind that not only Flask has the problem of not knowing
what subdomains are, your web browser does as well. Most modern web
browsers will not allow cross-subdomain cookies to be set on a
server name without dots in it. So if your server name is
``'localhost'`` you will not be able to set a cookie for
``'localhost'`` and every subdomain of it. Please choose a different
server name in that case, like ``'myapplication.local'`` and add
this name + the subdomains you want to use into your host config
or setup a local `bind`_.
.. py:data:: TESTING
.. _bind: https://www.isc.org/downloads/bind/
Enable testing mode. Exceptions are propagated rather than handled by the
the app's error handlers. Extensions may also change their behavior to
facilitate easier testing. You should enable this in your own tests.
Default: ``False``
.. py:data:: PROPAGATE_EXCEPTIONS
Exceptions are re-raised rather than being handled by the app's error
handlers. If not set, this is implicitly true if ``TESTING`` or ``DEBUG``
is enabled.
Default: ``None``
.. py:data:: PRESERVE_CONTEXT_ON_EXCEPTION
Don't pop the request context when an exception occurs. If not set, this
is true if ``DEBUG`` is true. This allows debuggers to introspect the
request data on errors, and should normally not need to be set directly.
Default: ``None``
.. py:data:: TRAP_HTTP_EXCEPTIONS
If there is no handler for an ``HTTPException``-type exception, re-raise it
to be handled by the interactive debugger instead of returning it as a
simple error response.
Default: ``False``
.. py:data:: TRAP_BAD_REQUEST_ERRORS``
Trying to access a key that doesn't exist from request dicts like ``args``
and ``form`` will return a 400 Bad Request error page. Enable this to treat
the error as an unhandled exception instead so that you get the interactive
debugger. This is a more specific version of ``TRAP_HTTP_EXCEPTIONS``. If
unset, it is enabled in debug mode.
Default: ``None``
.. py:data:: SECRET_KEY
A secret key that will be used for securely signing the session cookie
and can be used for any other security related needs by extensions or your
application. It should be a long random string of bytes, although unicode
is accepted too. For example, copy the output of this to your config::
python -c 'import os; print(os.urandom(32))'
**Do not reveal the secret key when posting questions or committing code.**
Default: ``None``
.. py:data:: SESSION_COOKIE_NAME
The name of the session cookie. Can be changed in case you already have a
cookie with the same name.
Default: ``'session'``
.. py:data:: SESSION_COOKIE_DOMAIN
The domain match rule that the session cookie will be valid for. If not
set, the cookie will be valid for all subdomains of ``SERVER_NAME``. If
``False``, the cookie's domain will not be set.
Default: ``None``
.. py:data:: SESSION_COOKIE_PATH
The path that the session cookie will be valid for. If not set, the cookie
will be valid underneath ``APPLICATION_ROOT`` or ``/`` if that is not set.
Default: ``None``
.. py:data:: SESSION_COOKIE_HTTPONLY
Browsers will not allow JavaScript access to cookies marked as "HTTP only"
for security.
Default: ``True``
.. py:data:: SESSION_COOKIE_SECURE
Browsers will only send cookies with requests over HTTPS if the cookie is
marked "secure". The application must be served over HTTPS for this to make
sense.
Default: ``False``
.. py:data:: PERMANENT_SESSION_LIFETIME
If ``session.permanent`` is true, the cookie's max age will be set to this
number of seconds. Can either be a :class:`datetime.timedelta` or an
``int``.
Default: ``timedelta(days=31)`` (``2678400`` seconds)
.. py:data:: SESSION_REFRESH_EACH_REQUEST
Control whether the cookie is sent with every response when
``session.permanent`` is true. Sending the cookie every time (the default)
can more reliably keep the session from expiring, but uses more bandwidth.
Non-permanent sessions are not affected.
Default: ``True``
.. py:data:: USE_X_SENDFILE
When serving files, set the ``X-Sendfile`` header instead of serving the
data with Flask. Some web servers, such as Apache, recognize this and serve
the data more efficiently. This only makes sense when using such a server.
Default: ``False``
.. py:data:: SEND_FILE_MAX_AGE_DEFAULT
When serving files, set the cache control max age to this number of
seconds. Can either be a :class:`datetime.timedelta` or an ``int``.
Override this value on a per-file basis using
:meth:`~flask.Flask.get_send_file_max_age` on the application or blueprint.
Default: ``timedelta(hours=12)`` (``43200`` seconds)
.. py:data:: LOGGER_NAME
The name of the logger that the Flask application sets up. If not set,
it will take the import name passed to ``Flask.__init__``.
Default: ``None``
.. py:data:: LOGGER_HANDLER_POLICY
When to activate the application's logger handler. ``'always'`` always
enables it, ``'debug'`` only activates it in debug mode, ``'production'``
only activates it when not in debug mode, and ``'never'`` never enables it.
Default: ``'always'``
.. py:data:: SERVER_NAME
Inform the application what host and port it is bound to. Required for
subdomain route matching support.
If set, will be used for the session cookie domain if
``SESSION_COOKIE_DOMAIN`` is not set. Modern web browsers will not allow
setting cookies for domains without a dot. To use a domain locally,
add any names that should route to the app to your ``hosts`` file. ::
127.0.0.1 localhost.dev
If set, ``url_for`` can generate external URLs with only an application
context instead of a request context.
Default: ``None``
.. py:data:: APPLICATION_ROOT
Inform the application what path it is mounted under by the application /
web server.
Will be used for the session cookie path if ``SESSION_COOKIE_PATH`` is not
set.
Default: ``'/'``
.. py:data:: PREFERRED_URL_SCHEME
Use this scheme for generating external URLs when not in a request context.
Default: ``'http'``
.. py:data:: MAX_CONTENT_LENGTH
Don't read more than this many bytes from the incoming request data. If not
set and the request does not specify a ``CONTENT_LENGTH``, no data will be
read for security.
Default: ``None``
.. py:data:: JSON_AS_ASCII
Serialize objects to ASCII-encoded JSON. If this is disabled, the JSON
will be returned as a Unicode string, or encoded as ``UTF-8`` by
``jsonify``. This has security implications when rendering the JSON in
to JavaScript in templates, and should typically remain enabled.
Default: ``True``
.. py:data:: JSON_SORT_KEYS
Sort the keys of JSON objects alphabetically. This is useful for caching
because it ensures the data is serialized the same way no matter what
Python's hash seed is. While not recommended, you can disable this for a
possible performance improvement at the cost of caching.
Default: ``True``
.. py:data:: JSONIFY_PRETTYPRINT_REGULAR
``jsonify`` responses will be output with newlines, spaces, and indentation
for easier reading by humans. Always enabled in debug mode.
Default: ``False``
.. py:data:: JSONIFY_MIMETYPE
The mimetype of ``jsonify`` responses.
Default: ``'application/json'``
.. py:data:: TEMPLATES_AUTO_RELOAD
Reload templates when they are changed. If not set, it will be enabled in
debug mode.
Default: ``None``
.. py:data:: EXPLAIN_TEMPLATE_LOADING
Log debugging information tracing how a template file was loaded. This can
be useful to figure out why a template was not loaded or the wrong file
appears to be loaded.
Default: ``False``
.. versionadded:: 0.4
``LOGGER_NAME``
@ -262,7 +345,7 @@ So a common pattern is this::
This first loads the configuration from the
`yourapplication.default_settings` module and then overrides the values
with the contents of the file the :envvar:``YOURAPPLICATION_SETTINGS``
with the contents of the file the :envvar:`YOURAPPLICATION_SETTINGS`
environment variable points to. This environment variable can be set on
Linux or OS X with the export command in the shell before starting the
server::
@ -463,3 +546,4 @@ Example usage for both::
# or via open_instance_resource:
with app.open_instance_resource('application.cfg') as f:
config = f.read()

1
docs/contents.rst.inc
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@ -59,3 +59,4 @@ Design notes, legal information and changelog are here for the interested.
upgrading
changelog
license
contributing

1
docs/contributing.rst Normal file
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@ -0,0 +1 @@
.. include:: ../CONTRIBUTING.rst

8
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@ -144,7 +144,7 @@ A basic FastCGI configuration for lighttpd looks like that::
)
alias.url = (
"/static/" => "/path/to/your/static"
"/static/" => "/path/to/your/static/"
)
url.rewrite-once = (
@ -159,7 +159,7 @@ work in the URL root you have to work around a lighttpd bug with the
Make sure to apply it only if you are mounting the application the URL
root. Also, see the Lighty docs for more information on `FastCGI and Python
<http://redmine.lighttpd.net/projects/lighttpd/wiki/Docs_ModFastCGI>`_ (note that
<https://redmine.lighttpd.net/projects/lighttpd/wiki/Docs_ModFastCGI>`_ (note that
explicitly passing a socket to run() is no longer necessary).
Configuring nginx
@ -234,7 +234,7 @@ python path. Common problems are:
web server.
- Different python interpreters being used.
.. _nginx: http://nginx.org/
.. _lighttpd: http://www.lighttpd.net/
.. _nginx: https://nginx.org/
.. _lighttpd: https://www.lighttpd.net/
.. _cherokee: http://cherokee-project.com/
.. _flup: https://pypi.python.org/pypi/flup

4
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@ -21,8 +21,10 @@ Hosted options
- `Deploying Flask on OpenShift <https://developers.openshift.com/en/python-flask.html>`_
- `Deploying Flask on Webfaction <http://flask.pocoo.org/snippets/65/>`_
- `Deploying Flask on Google App Engine <https://github.com/kamalgill/flask-appengine-template>`_
- `Deploying Flask on AWS Elastic Beanstalk <https://docs.aws.amazon.com/elasticbeanstalk/latest/dg/create-deploy-python-flask.html>`_
- `Sharing your Localhost Server with Localtunnel <http://flask.pocoo.org/snippets/89/>`_
- `Deploying on Azure (IIS) <https://azure.microsoft.com/documentation/articles/web-sites-python-configure/>`_
- `Deploying on PythonAnywhere <https://help.pythonanywhere.com/pages/Flask/>`_
Self-hosted options
-------------------
@ -30,8 +32,8 @@ Self-hosted options
.. toctree::
:maxdepth: 2
mod_wsgi
wsgi-standalone
uwsgi
mod_wsgi
fastcgi
cgi

12
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@ -13,7 +13,7 @@ If you are using the `Apache`_ webserver, consider using `mod_wsgi`_.
not called because this will always start a local WSGI server which
we do not want if we deploy that application to mod_wsgi.
.. _Apache: http://httpd.apache.org/
.. _Apache: https://httpd.apache.org/
Installing `mod_wsgi`
---------------------
@ -114,7 +114,7 @@ refuse to run with the above configuration. On a Windows system, eliminate those
Note: There have been some changes in access control configuration for `Apache 2.4`_.
.. _Apache 2.4: http://httpd.apache.org/docs/trunk/upgrading.html
.. _Apache 2.4: https://httpd.apache.org/docs/trunk/upgrading.html
Most notably, the syntax for directory permissions has changed from httpd 2.2
@ -130,12 +130,12 @@ to httpd 2.4 syntax
Require all granted
For more information consult the `mod_wsgi wiki`_.
For more information consult the `mod_wsgi documentation`_.
.. _mod_wsgi: http://code.google.com/p/modwsgi/
.. _installation instructions: http://code.google.com/p/modwsgi/wiki/QuickInstallationGuide
.. _mod_wsgi: https://github.com/GrahamDumpleton/mod_wsgi
.. _installation instructions: https://modwsgi.readthedocs.io/en/develop/installation.html
.. _virtual python: https://pypi.python.org/pypi/virtualenv
.. _mod_wsgi wiki: http://code.google.com/p/modwsgi/w/list
.. _mod_wsgi documentation: https://modwsgi.readthedocs.io/en/develop/index.html
Troubleshooting
---------------

4
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@ -66,7 +66,7 @@ to have it in the URL root its a bit simpler::
uwsgi_pass unix:/tmp/yourapplication.sock;
}
.. _nginx: http://nginx.org/
.. _lighttpd: http://www.lighttpd.net/
.. _nginx: https://nginx.org/
.. _lighttpd: https://www.lighttpd.net/
.. _cherokee: http://cherokee-project.com/
.. _uwsgi: http://projects.unbit.it/uwsgi/

16
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@ -27,6 +27,22 @@ For example, to run a Flask application with 4 worker processes (``-w
.. _eventlet: http://eventlet.net/
.. _greenlet: https://greenlet.readthedocs.io/en/latest/
uWSGI
--------
`uWSGI`_ is a fast application server written in C. It is very configurable
which makes it more complicated to setup than gunicorn.
Running `uWSGI HTTP Router`_::
uwsgi --http 127.0.0.1:5000 --module myproject:app
For a more optimized setup, see `configuring uWSGI and NGINX`_.
.. _uWSGI: http://uwsgi-docs.readthedocs.io/en/latest/
.. _uWSGI HTTP Router: http://uwsgi-docs.readthedocs.io/en/latest/HTTP.html#the-uwsgi-http-https-router
.. _configuring uWSGI and NGINX: uwsgi.html#starting-your-app-with-uwsgi
Gevent
-------

84
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@ -34,7 +34,7 @@ Error Logging Tools
Sending error mails, even if just for critical ones, can become
overwhelming if enough users are hitting the error and log files are
typically never looked at. This is why we recommend using `Sentry
<http://www.getsentry.com/>`_ for dealing with application errors. It's
<https://www.getsentry.com/>`_ for dealing with application errors. It's
available as an Open Source project `on GitHub
<https://github.com/getsentry/sentry>`__ and is also available as a `hosted version
<https://getsentry.com/signup/>`_ which you can try for free. Sentry
@ -51,7 +51,7 @@ And then add this to your Flask app::
from raven.contrib.flask import Sentry
sentry = Sentry(app, dsn='YOUR_DSN_HERE')
Of if you are using factories you can also init it later::
Or if you are using factories you can also init it later::
from raven.contrib.flask import Sentry
sentry = Sentry(dsn='YOUR_DSN_HERE')
@ -76,49 +76,72 @@ Error handlers
You might want to show custom error pages to the user when an error occurs.
This can be done by registering error handlers.
Error handlers are normal :ref:`views` but instead of being registered for
routes they are registered for exceptions that are rised while trying to
do something else.
An error handler is a normal view function that return a response, but instead
of being registered for a route, it is registered for an exception or HTTP
status code that would is raised while trying to handle a request.
Registering
```````````
Register error handlers using :meth:`~flask.Flask.errorhandler` or
:meth:`~flask.Flask.register_error_handler`::
Register handlers by decorating a function with
:meth:`~flask.Flask.errorhandler`. Or use
:meth:`~flask.Flask.register_error_handler` to register the function later.
Remember to set the error code when returning the response. ::
@app.errorhandler(werkzeug.exceptions.BadRequest)
def handle_bad_request(e):
return 'bad request!'
app.register_error_handler(400, lambda e: 'bad request!')
return 'bad request!', 400
# or, without the decorator
app.register_error_handler(400, handle_bad_request)
Those two ways are equivalent, but the first one is more clear and leaves
you with a function to call on your whim (and in tests). Note that
:exc:`werkzeug.exceptions.HTTPException` subclasses like
:exc:`~werkzeug.exceptions.BadRequest` from the example and their HTTP codes
are interchangeable when handed to the registration methods or decorator
(``BadRequest.code == 400``).
:exc:`~werkzeug.exceptions.BadRequest` and their HTTP codes are interchangeable
when registering handlers. (``BadRequest.code == 400``)
You are however not limited to :exc:`~werkzeug.exceptions.HTTPException`
or HTTP status codes but can register a handler for every exception class you
like.
Non-standard HTTP codes cannot be registered by code because they are not known
by Werkzeug. Instead, define a subclass of
:class:`~werkzeug.exceptions.HTTPException` with the appropriate code and
register and raise that exception class. ::
.. versionchanged:: 0.11
class InsufficientStorage(werkzeug.exceptions.HTTPException):
code = 507
description = 'Not enough storage space.'
Errorhandlers are now prioritized by specificity of the exception classes
they are registered for instead of the order they are registered in.
app.register_error_handler(InsuffcientStorage, handle_507)
raise InsufficientStorage()
Handlers can be registered for any exception class, not just
:exc:`~werkzeug.exceptions.HTTPException` subclasses or HTTP status
codes. Handlers can be registered for a specific class, or for all subclasses
of a parent class.
Handling
````````
Once an exception instance is raised, its class hierarchy is traversed,
and searched for in the exception classes for which handlers are registered.
The most specific handler is selected.
When an exception is caught by Flask while handling a request, it is first
looked up by code. If no handler is registered for the code, it is looked up
by its class hierarchy; the most specific handler is chosen. If no handler is
registered, :class:`~werkzeug.exceptions.HTTPException` subclasses show a
generic message about their code, while other exceptions are converted to a
generic 500 Internal Server Error.
E.g. if an instance of :exc:`ConnectionRefusedError` is raised, and a handler
For example, if an instance of :exc:`ConnectionRefusedError` is raised, and a handler
is registered for :exc:`ConnectionError` and :exc:`ConnectionRefusedError`,
the more specific :exc:`ConnectionRefusedError` handler is called on the
exception instance, and its response is shown to the user.
the more specific :exc:`ConnectionRefusedError` handler is called with the
exception instance to generate the response.
Handlers registered on the blueprint take precedence over those registered
globally on the application, assuming a blueprint is handling the request that
raises the exception. However, the blueprint cannot handle 404 routing errors
because the 404 occurs at the routing level before the blueprint can be
determined.
.. versionchanged:: 0.11
Handlers are prioritized by specificity of the exception classes they are
registered for instead of the order they are registered in.
Error Mails
-----------
@ -216,7 +239,7 @@ A formatter can be instantiated with a format string. Note that
tracebacks are appended to the log entry automatically. You don't have to
do that in the log formatter format string.
Here some example setups:
Here are some example setups:
Email
`````
@ -276,8 +299,9 @@ that this list is not complete, consult the official documentation of the
| ``%(lineno)d`` | Source line number where the logging call was |
| | issued (if available). |
+------------------+----------------------------------------------------+
| ``%(asctime)s`` | Human-readable time when the LogRecord` was |
| | created. By default this is of the form |
| ``%(asctime)s`` | Human-readable time when the |
| | :class:`~logging.LogRecord` was created. |
| | By default this is of the form |
| | ``"2003-07-08 16:49:45,896"`` (the numbers after |
| | the comma are millisecond portion of the time). |
| | This can be changed by subclassing the formatter |

40
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@ -29,12 +29,6 @@ be something like "Flask-SimpleXML". Make sure to include the name
This is how users can then register dependencies to your extension in
their :file:`setup.py` files.
Flask sets up a redirect package called :data:`flask.ext` where users
should import the extensions from. If you for instance have a package
called ``flask_something`` users would import it as
``flask.ext.something``. This is done to transition from the old
namespace packages. See :ref:`ext-import-transition` for more details.
But what do extensions look like themselves? An extension has to ensure
that it works with multiple Flask application instances at once. This is
a requirement because many people will use patterns like the
@ -48,7 +42,7 @@ that people can easily install the development version into their
virtualenv without having to download the library by hand.
Flask extensions must be licensed under a BSD, MIT or more liberal license
to be able to be enlisted in the Flask Extension Registry. Keep in mind
in order to be listed in the Flask Extension Registry. Keep in mind
that the Flask Extension Registry is a moderated place and libraries will
be reviewed upfront if they behave as required.
@ -154,10 +148,10 @@ What to use depends on what you have in mind. For the SQLite 3 extension
we will use the class-based approach because it will provide users with an
object that handles opening and closing database connections.
What's important about classes is that they encourage to be shared around
on module level. In that case, the object itself must not under any
When designing your classes, it's important to make them easily reusable
at the module level. This means the object itself must not under any
circumstances store any application specific state and must be shareable
between different application.
between different applications.
The Extension Code
------------------
@ -334,10 +328,10 @@ development. If you want to learn more, it's a very good idea to check
out existing extensions on the `Flask Extension Registry`_. If you feel
lost there is still the `mailinglist`_ and the `IRC channel`_ to get some
ideas for nice looking APIs. Especially if you do something nobody before
you did, it might be a very good idea to get some more input. This not
only to get an idea about what people might want to have from an
extension, but also to avoid having multiple developers working on pretty
much the same side by side.
you did, it might be a very good idea to get some more input. This not only
generates useful feedback on what people might want from an extension, but
also avoids having multiple developers working in isolation on pretty much the
same problem.
Remember: good API design is hard, so introduce your project on the
mailinglist, and let other developers give you a helping hand with
@ -370,10 +364,10 @@ extension to be approved you have to follow these guidelines:
3. APIs of approved extensions will be checked for the following
characteristics:
- an approved extension has to support multiple applications
running in the same Python process.
- it must be possible to use the factory pattern for creating
applications.
- an approved extension has to support multiple applications
running in the same Python process.
- it must be possible to use the factory pattern for creating
applications.
4. The license must be BSD/MIT/WTFPL licensed.
5. The naming scheme for official extensions is *Flask-ExtensionName* or
@ -387,13 +381,11 @@ extension to be approved you have to follow these guidelines:
link to the documentation, website (if there is one) and there
must be a link to automatically install the development version
(``PackageName==dev``).
9. The ``zip_safe`` flag in the setup script must be set to ``False``,
even if the extension would be safe for zipping.
10. An extension currently has to support Python 2.6 as well as
Python 2.7
9. The ``zip_safe`` flag in the setup script must be set to ``False``,
even if the extension would be safe for zipping.
10. An extension currently has to support Python 2.7, Python 3.3 and higher.
.. _ext-import-transition:
Extension Import Transition
---------------------------
@ -413,6 +405,6 @@ schema. The ``flask.ext.foo`` compatibility alias is still in Flask 0.11 but is
now deprecated -- you should use ``flask_foo``.
.. _OAuth extension: http://pythonhosted.org/Flask-OAuth/
.. _OAuth extension: https://pythonhosted.org/Flask-OAuth/
.. _mailinglist: http://flask.pocoo.org/mailinglist/
.. _IRC channel: http://flask.pocoo.org/community/irc/

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@ -1,86 +0,0 @@
# flasky extensions. flasky pygments style based on tango style
from pygments.style import Style
from pygments.token import Keyword, Name, Comment, String, Error, \
Number, Operator, Generic, Whitespace, Punctuation, Other, Literal
class FlaskyStyle(Style):
background_color = "#f8f8f8"
default_style = ""
styles = {
# No corresponding class for the following:
#Text: "", # class: ''
Whitespace: "underline #f8f8f8", # class: 'w'
Error: "#a40000 border:#ef2929", # class: 'err'
Other: "#000000", # class 'x'
Comment: "italic #8f5902", # class: 'c'
Comment.Preproc: "noitalic", # class: 'cp'
Keyword: "bold #004461", # class: 'k'
Keyword.Constant: "bold #004461", # class: 'kc'
Keyword.Declaration: "bold #004461", # class: 'kd'
Keyword.Namespace: "bold #004461", # class: 'kn'
Keyword.Pseudo: "bold #004461", # class: 'kp'
Keyword.Reserved: "bold #004461", # class: 'kr'
Keyword.Type: "bold #004461", # class: 'kt'
Operator: "#582800", # class: 'o'
Operator.Word: "bold #004461", # class: 'ow' - like keywords
Punctuation: "bold #000000", # class: 'p'
# because special names such as Name.Class, Name.Function, etc.
# are not recognized as such later in the parsing, we choose them
# to look the same as ordinary variables.
Name: "#000000", # class: 'n'
Name.Attribute: "#c4a000", # class: 'na' - to be revised
Name.Builtin: "#004461", # class: 'nb'
Name.Builtin.Pseudo: "#3465a4", # class: 'bp'
Name.Class: "#000000", # class: 'nc' - to be revised
Name.Constant: "#000000", # class: 'no' - to be revised
Name.Decorator: "#888", # class: 'nd' - to be revised
Name.Entity: "#ce5c00", # class: 'ni'
Name.Exception: "bold #cc0000", # class: 'ne'
Name.Function: "#000000", # class: 'nf'
Name.Property: "#000000", # class: 'py'
Name.Label: "#f57900", # class: 'nl'
Name.Namespace: "#000000", # class: 'nn' - to be revised
Name.Other: "#000000", # class: 'nx'
Name.Tag: "bold #004461", # class: 'nt' - like a keyword
Name.Variable: "#000000", # class: 'nv' - to be revised
Name.Variable.Class: "#000000", # class: 'vc' - to be revised
Name.Variable.Global: "#000000", # class: 'vg' - to be revised
Name.Variable.Instance: "#000000", # class: 'vi' - to be revised
Number: "#990000", # class: 'm'
Literal: "#000000", # class: 'l'
Literal.Date: "#000000", # class: 'ld'
String: "#4e9a06", # class: 's'
String.Backtick: "#4e9a06", # class: 'sb'
String.Char: "#4e9a06", # class: 'sc'
String.Doc: "italic #8f5902", # class: 'sd' - like a comment
String.Double: "#4e9a06", # class: 's2'
String.Escape: "#4e9a06", # class: 'se'
String.Heredoc: "#4e9a06", # class: 'sh'
String.Interpol: "#4e9a06", # class: 'si'
String.Other: "#4e9a06", # class: 'sx'
String.Regex: "#4e9a06", # class: 'sr'
String.Single: "#4e9a06", # class: 's1'
String.Symbol: "#4e9a06", # class: 'ss'
Generic: "#000000", # class: 'g'
Generic.Deleted: "#a40000", # class: 'gd'
Generic.Emph: "italic #000000", # class: 'ge'
Generic.Error: "#ef2929", # class: 'gr'
Generic.Heading: "bold #000080", # class: 'gh'
Generic.Inserted: "#00A000", # class: 'gi'
Generic.Output: "#888", # class: 'go'
Generic.Prompt: "#745334", # class: 'gp'
Generic.Strong: "bold #000000", # class: 'gs'
Generic.Subheading: "bold #800080", # class: 'gu'
Generic.Traceback: "bold #a40000", # class: 'gt'
}

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@ -3,163 +3,173 @@
Installation
============
Flask depends on some external libraries, like `Werkzeug
<http://werkzeug.pocoo.org/>`_ and `Jinja2 <http://jinja.pocoo.org/>`_.
Werkzeug is a toolkit for WSGI, the standard Python interface between web
applications and a variety of servers for both development and deployment.
Jinja2 renders templates.
Python Version
--------------
So how do you get all that on your computer quickly? There are many ways you
could do that, but the most kick-ass method is virtualenv, so let's have a look
at that first.
We recommend using the latest version of Python 3. Flask supports Python 3.3
and newer, Python 2.6 and newer, and PyPy.
You will need Python 2.6 or newer to get started, so be sure to have an
up-to-date Python 2.x installation. For using Flask with Python 3 have a
look at :ref:`python3-support`.
Dependencies
------------
.. _virtualenv:
These distributions will be installed automatically when installing Flask.
virtualenv
----------
* `Werkzeug`_ implements WSGI, the standard Python interface between
applications and servers.
* `Jinja`_ is a template language that renders the pages your application
serves.
* `MarkupSafe`_ comes with Jinja. It escapes untrusted input when rendering
templates to avoid injection attacks.
* `ItsDangerous`_ securely signs data to ensure its integrity. This is used
to protect Flask's session cookie.
* `Click`_ is a framework for writing command line applications. It provides
the ``flask`` command and allows adding custom management commands.
Virtualenv is probably what you want to use during development, and if you have
shell access to your production machines, you'll probably want to use it there,
too.
.. _Werkzeug: http://werkzeug.pocoo.org/
.. _Jinja: http://jinja.pocoo.org/
.. _MarkupSafe: https://pypi.python.org/pypi/MarkupSafe
.. _ItsDangerous: https://pythonhosted.org/itsdangerous/
.. _Click: http://click.pocoo.org/
What problem does virtualenv solve? If you like Python as much as I do,
chances are you want to use it for other projects besides Flask-based web
applications. But the more projects you have, the more likely it is that you
will be working with different versions of Python itself, or at least different
versions of Python libraries. Let's face it: quite often libraries break
backwards compatibility, and it's unlikely that any serious application will
have zero dependencies. So what do you do if two or more of your projects have
conflicting dependencies?
Optional dependencies
~~~~~~~~~~~~~~~~~~~~~
Virtualenv to the rescue! Virtualenv enables multiple side-by-side
installations of Python, one for each project. It doesn't actually install
separate copies of Python, but it does provide a clever way to keep different
project environments isolated. Let's see how virtualenv works.
These distributions will not be installed automatically. Flask will detect and
use them if you install them.
If you are on Mac OS X or Linux, chances are that the following
command will work for you::
* `Blinker`_ provides support for :ref:`signals`.
* `SimpleJSON`_ is a fast JSON implementation that is compatible with
Python's ``json`` module. It is preferred for JSON operations if it is
installed.
$ sudo pip install virtualenv
.. _Blinker: https://pythonhosted.org/blinker/
.. _SimpleJSON: https://simplejson.readthedocs.io/
It will probably install virtualenv on your system. Maybe it's even
in your package manager. If you use Ubuntu, try::
Virtual environments
--------------------
$ sudo apt-get install python-virtualenv
Use a virtual environment to manage the dependencies for your project, both in
development and in production.
If you are on Windows and don't have the ``easy_install`` command, you must
install it first. Check the :ref:`windows-easy-install` section for more
information about how to do that. Once you have it installed, run the same
commands as above, but without the ``sudo`` prefix.
What problem does a virtual environment solve? The more Python projects you
have, the more likely it is that you need to work with different versions of
Python libraries, or even Python itself. Newer versions of libraries for one
project can break compatibility in another project.
Once you have virtualenv installed, just fire up a shell and create
your own environment. I usually create a project folder and a :file:`venv`
folder within::
Virtual environments are independent groups of Python libraries, one for each
project. Packages installed for one project will not affect other projects or
the operating system's packages.
$ mkdir myproject
$ cd myproject
$ virtualenv venv
New python executable in venv/bin/python
Installing setuptools, pip............done.
Python 3 comes bundled with the :mod:`venv` module to create virtual
environments. If you're using a modern version of Python, you can continue on
to the next section.
Now, whenever you want to work on a project, you only have to activate the
corresponding environment. On OS X and Linux, do the following::
If you're using Python 2, see :ref:`install-install-virtualenv` first.
$ . venv/bin/activate
.. _install-create-env:
If you are a Windows user, the following command is for you::
Create an environment
~~~~~~~~~~~~~~~~~~~~~
$ venv\scripts\activate
Create a project folder and a :file:`venv` folder within:
Either way, you should now be using your virtualenv (notice how the prompt of
your shell has changed to show the active environment).
.. code-block:: sh
And if you want to go back to the real world, use the following command::
mkdir myproject
cd myproject
python3 -m venv venv
$ deactivate
On Windows:
After doing this, the prompt of your shell should be as familiar as before.
.. code-block:: bat
Now, let's move on. Enter the following command to get Flask activated in your
virtualenv::
py -3 -m venv venv
$ pip install Flask
If you needed to install virtualenv because you are on an older version of
Python, use the following command instead:
A few seconds later and you are good to go.
.. code-block:: sh
virtualenv venv
System-Wide Installation
------------------------
On Windows:
This is possible as well, though I do not recommend it. Just run
``pip`` with root privileges::
.. code-block:: bat
$ sudo pip install Flask
\Python27\Scripts\virtualenv.exe venv
(On Windows systems, run it in a command-prompt window with administrator
privileges, and leave out ``sudo``.)
Activate the environment
~~~~~~~~~~~~~~~~~~~~~~~~
Before you work on your project, activate the corresponding environment:
Living on the Edge
.. code-block:: sh
. venv/bin/activate
On Windows:
.. code-block:: bat
venv\Scripts\activate
Your shell prompt will change to show the name of the activated environment.
Install Flask
-------------
Within the activated environment, use the following command to install Flask:
.. code-block:: sh
pip install Flask
Living on the edge
~~~~~~~~~~~~~~~~~~
If you want to work with the latest Flask code before it's released, install or
update the code from the master branch:
.. code-block:: sh
pip install -U https://github.com/pallets/flask/archive/master.tar.gz
.. _install-install-virtualenv:
Install virtualenv
------------------
If you want to work with the latest version of Flask, there are two ways: you
can either let ``pip`` pull in the development version, or you can tell
it to operate on a git checkout. Either way, virtualenv is recommended.
If you are using Python 2, the venv module is not available. Instead,
install `virtualenv`_.
Get the git checkout in a new virtualenv and run in development mode::
On Linux, virtualenv is provided by your package manager:
$ git clone http://github.com/pallets/flask.git
Initialized empty Git repository in ~/dev/flask/.git/
$ cd flask
$ virtualenv venv
New python executable in venv/bin/python
Installing setuptools, pip............done.
$ . venv/bin/activate
$ python setup.py develop
...
Finished processing dependencies for Flask
.. code-block:: sh
This will pull in the dependencies and activate the git head as the current
version inside the virtualenv. Then all you have to do is run ``git pull
origin`` to update to the latest version.
# Debian, Ubuntu
sudo apt-get install python-virtualenv
.. _windows-easy-install:
# CentOS, Fedora
sudo yum install python-virtualenv
`pip` and `setuptools` on Windows
---------------------------------
# Arch
sudo pacman -S python-virtualenv
Sometimes getting the standard "Python packaging tools" like ``pip``, ``setuptools``
and ``virtualenv`` can be a little trickier, but nothing very hard. The crucial
package you will need is pip - this will let you install
anything else (like virtualenv). Fortunately there is a "bootstrap script"
you can run to install.
If you are on Mac OS X or Windows, download `get-pip.py`_, then:
If you don't currently have ``pip``, then `get-pip.py` will install it for you.
.. code-block:: sh
`get-pip.py`_
sudo python2 Downloads/get-pip.py
sudo python2 -m pip install virtualenv
It should be double-clickable once you download it. If you already have ``pip``,
you can upgrade them by running::
On Windows, as an administrator:
> pip install --upgrade pip setuptools
.. code-block:: bat
Most often, once you pull up a command prompt you want to be able to type ``pip``
and ``python`` which will run those things, but this might not automatically happen
on Windows, because it doesn't know where those executables are (give either a try!).
\Python27\python.exe Downloads\get-pip.py
\Python27\python.exe -m pip install virtualenv
To fix this, you should be able to navigate to your Python install directory
(e.g :file:`C:\Python27`), then go to :file:`Tools`, then :file:`Scripts`, then find the
:file:`win_add2path.py` file and run that. Open a **new** Command Prompt and
check that you can now just type ``python`` to bring up the interpreter.
Finally, to install `virtualenv`_, you can simply run::
> pip install virtualenv
Then you can be off on your way following the installation instructions above.
Now you can continue to :ref:`install-create-env`.
.. _virtualenv: https://virtualenv.pypa.io/
.. _get-pip.py: https://bootstrap.pypa.io/get-pip.py

4
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@ -6,7 +6,7 @@ Application Factories
If you are already using packages and blueprints for your application
(:ref:`blueprints`) there are a couple of really nice ways to further improve
the experience. A common pattern is creating the application object when
the blueprint is imported. But if you move the creation of this object,
the blueprint is imported. But if you move the creation of this object
into a function, you can then create multiple instances of this app later.
So why would you want to do this?
@ -60,7 +60,7 @@ Factories & Extensions
It's preferable to create your extensions and app factories so that the
extension object does not initially get bound to the application.
Using `Flask-SQLAlchemy <http://pythonhosted.org/Flask-SQLAlchemy/>`_,
Using `Flask-SQLAlchemy <http://flask-sqlalchemy.pocoo.org/>`_,
as an example, you should not do something along those lines::
def create_app(config_filename):

80
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@ -1,24 +1,27 @@
Celery Based Background Tasks
=============================
Celery Background Tasks
=======================
Celery is a task queue for Python with batteries included. It used to
have a Flask integration but it became unnecessary after some
restructuring of the internals of Celery with Version 3. This guide fills
in the blanks in how to properly use Celery with Flask but assumes that
you generally already read the `First Steps with Celery
<http://docs.celeryproject.org/en/latest/getting-started/first-steps-with-celery.html>`_
guide in the official Celery documentation.
If your application has a long running task, such as processing some uploaded
data or sending email, you don't want to wait for it to finish during a
request. Instead, use a task queue to send the necessary data to another
process that will run the task in the background while the request returns
immediately.
Installing Celery
-----------------
Celery is a powerful task queue that can be used for simple background tasks
as well as complex multi-stage programs and schedules. This guide will show you
how to configure Celery using Flask, but assumes you've already read the
`First Steps with Celery <http://docs.celeryproject.org/en/latest/getting-started/first-steps-with-celery.html>`_
guide in the Celery documentation.
Celery is on the Python Package Index (PyPI), so it can be installed with
standard Python tools like :command:`pip` or :command:`easy_install`::
Install
-------
Celery is a separate Python package. Install it from PyPI using pip::
$ pip install celery
Configuring Celery
------------------
Configure
---------
The first thing you need is a Celery instance, this is called the celery
application. It serves the same purpose as the :class:`~flask.Flask`
@ -36,15 +39,18 @@ This is all that is necessary to properly integrate Celery with Flask::
from celery import Celery
def make_celery(app):
celery = Celery(app.import_name, backend=app.config['CELERY_BACKEND'],
broker=app.config['CELERY_BROKER_URL'])
celery = Celery(
app.import_name,
backend=app.config['CELERY_RESULT_BACKEND'],
broker=app.config['CELERY_BROKER_URL']
)
celery.conf.update(app.config)
TaskBase = celery.Task
class ContextTask(TaskBase):
abstract = True
class ContextTask(celery.Task):
def __call__(self, *args, **kwargs):
with app.app_context():
return TaskBase.__call__(self, *args, **kwargs)
return self.run(*args, **kwargs)
celery.Task = ContextTask
return celery
@ -53,11 +59,12 @@ from the application config, updates the rest of the Celery config from
the Flask config and then creates a subclass of the task that wraps the
task execution in an application context.
Minimal Example
An example task
---------------
With what we have above this is the minimal example of using Celery with
Flask::
Let's write a task that adds two numbers together and returns the result. We
configure Celery's broker and backend to use Redis, create a ``celery``
application using the factor from above, and then use it to define the task. ::
from flask import Flask
@ -68,26 +75,27 @@ Flask::
)
celery = make_celery(flask_app)
@celery.task()
def add_together(a, b):
return a + b
This task can now be called in the background:
This task can now be called in the background::
>>> result = add_together.delay(23, 42)
>>> result.wait()
65
result = add_together.delay(23, 42)
result.wait() # 65
Running the Celery Worker
-------------------------
Run a worker
------------
Now if you jumped in and already executed the above code you will be
disappointed to learn that your ``.wait()`` will never actually return.
That's because you also need to run celery. You can do that by running
celery as a worker::
If you jumped in and already executed the above code you will be
disappointed to learn that ``.wait()`` will never actually return.
That's because you also need to run a Celery worker to receive and execute the
task. ::
$ celery -A your_application.celery worker
The ``your_application`` string has to point to your application's package
or module that creates the `celery` object.
or module that creates the ``celery`` object.
Now that the worker is running, ``wait`` will return the result once the task
is finished.

76
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@ -3,71 +3,43 @@
Deferred Request Callbacks
==========================
One of the design principles of Flask is that response objects are created
and passed down a chain of potential callbacks that can modify them or
replace them. When the request handling starts, there is no response
object yet. It is created as necessary either by a view function or by
some other component in the system.
One of the design principles of Flask is that response objects are created and
passed down a chain of potential callbacks that can modify them or replace
them. When the request handling starts, there is no response object yet. It is
created as necessary either by a view function or by some other component in
the system.
But what happens if you want to modify the response at a point where the
response does not exist yet? A common example for that would be a
before-request function that wants to set a cookie on the response object.
What happens if you want to modify the response at a point where the response
does not exist yet? A common example for that would be a
:meth:`~flask.Flask.before_request` callback that wants to set a cookie on the
response object.
One way is to avoid the situation. Very often that is possible. For
instance you can try to move that logic into an after-request callback
instead. Sometimes however moving that code there is just not a very
pleasant experience or makes code look very awkward.
One way is to avoid the situation. Very often that is possible. For instance
you can try to move that logic into a :meth:`~flask.Flask.after_request`
callback instead. However, sometimes moving code there makes it more
more complicated or awkward to reason about.
As an alternative possibility you can attach a bunch of callback functions
to the :data:`~flask.g` object and call them at the end of the request.
This way you can defer code execution from anywhere in the application.
The Decorator
-------------
The following decorator is the key. It registers a function on a list on
the :data:`~flask.g` object::
from flask import g
def after_this_request(f):
if not hasattr(g, 'after_request_callbacks'):
g.after_request_callbacks = []
g.after_request_callbacks.append(f)
return f
Calling the Deferred
--------------------
Now you can use the `after_this_request` decorator to mark a function to
be called at the end of the request. But we still need to call them. For
this the following function needs to be registered as
:meth:`~flask.Flask.after_request` callback::
@app.after_request
def call_after_request_callbacks(response):
for callback in getattr(g, 'after_request_callbacks', ()):
callback(response)
return response
A Practical Example
-------------------
As an alternative, you can use :func:`~flask.after_this_request` to register
callbacks that will execute after only the current request. This way you can
defer code execution from anywhere in the application, based on the current
request.
At any time during a request, we can register a function to be called at the
end of the request. For example you can remember the current language of the
user in a cookie in the before-request function::
end of the request. For example you can remember the current language of the
user in a cookie in a :meth:`~flask.Flask.before_request` callback::
from flask import request
from flask import request, after_this_request
@app.before_request
def detect_user_language():
language = request.cookies.get('user_lang')
if language is None:
language = guess_language_from_request()
# when the response exists, set a cookie with the language
@after_this_request
def remember_language(response):
response.set_cookie('user_lang', language)
g.language = language

2
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@ -174,4 +174,4 @@ the code without having to run ``install`` again after each change.
.. _pip: https://pypi.python.org/pypi/pip
.. _Setuptools: https://pythonhosted.org/setuptools
.. _Setuptools: https://pypi.python.org/pypi/setuptools

54
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@ -47,37 +47,53 @@ even if the application behaves correctly:
Error Handlers
--------------
An error handler is a function, just like a view function, but it is
called when an error happens and is passed that error. The error is most
likely a :exc:`~werkzeug.exceptions.HTTPException`, but in one case it
can be a different error: a handler for internal server errors will be
passed other exception instances as well if they are uncaught.
An error handler is a function that returns a response when a type of error is
raised, similar to how a view is a function that returns a response when a
request URL is matched. It is passed the instance of the error being handled,
which is most likely a :exc:`~werkzeug.exceptions.HTTPException`. An error
handler for "500 Internal Server Error" will be passed uncaught exceptions in
addition to explicit 500 errors.
An error handler is registered with the :meth:`~flask.Flask.errorhandler`
decorator and the error code of the exception. Keep in mind that Flask
will *not* set the error code for you, so make sure to also provide the
HTTP status code when returning a response.
decorator or the :meth:`~flask.Flask.register_error_handler` method. A handler
can be registered for a status code, like 404, or for an exception class.
Please note that if you add an error handler for "500 Internal Server
Error", Flask will not trigger it if it's running in Debug mode.
The status code of the response will not be set to the handler's code. Make
sure to provide the appropriate HTTP status code when returning a response from
a handler.
Here an example implementation for a "404 Page Not Found" exception::
A handler for "500 Internal Server Error" will not be used when running in
debug mode. Instead, the interactive debugger will be shown.
Here is an example implementation for a "404 Page Not Found" exception::
from flask import render_template
@app.errorhandler(404)
def page_not_found(e):
# note that we set the 404 status explicitly
return render_template('404.html'), 404
When using the :ref:`application factory pattern <app-factories>`::
from flask import Flask, render_template
def page_not_found(e):
return render_template('404.html'), 404
def create_app(config_filename):
app = Flask(__name__)
app.register_error_handler(404, page_not_found)
return app
An example template might be this:
.. sourcecode:: html+jinja
{% extends "layout.html" %}
{% block title %}Page Not Found{% endblock %}
{% block body %}
<h1>Page Not Found</h1>
<p>What you were looking for is just not there.
<p><a href="{{ url_for('index') }}">go somewhere nice</a>
{% endblock %}
{% extends "layout.html" %}
{% block title %}Page Not Found{% endblock %}
{% block body %}
<h1>Page Not Found</h1>
<p>What you were looking for is just not there.
<p><a href="{{ url_for('index') }}">go somewhere nice</a>
{% endblock %}

2
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@ -49,5 +49,5 @@ web server's documentation.
See also
--------
* The `Favicon <http://en.wikipedia.org/wiki/Favicon>`_ article on
* The `Favicon <https://en.wikipedia.org/wiki/Favicon>`_ article on
Wikipedia

10
docs/patterns/fileuploads.rst
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@ -21,7 +21,7 @@ specific upload folder and displays a file to the user. Let's look at the
bootstrapping code for our application::
import os
from flask import Flask, request, redirect, url_for
from flask import Flask, flash, request, redirect, url_for
from werkzeug.utils import secure_filename
UPLOAD_FOLDER = '/path/to/the/uploads'
@ -58,7 +58,7 @@ the file and redirects the user to the URL for the uploaded file::
return redirect(request.url)
file = request.files['file']
# if user does not select file, browser also
# submit a empty part without filename
# submit an empty part without filename
if file.filename == '':
flash('No selected file')
return redirect(request.url)
@ -72,8 +72,8 @@ the file and redirects the user to the URL for the uploaded file::
<title>Upload new File</title>
<h1>Upload new File</h1>
<form method=post enctype=multipart/form-data>
<p><input type=file name=file>
<input type=submit value=Upload>
<input type=file name=file>
<input type=submit value=Upload>
</form>
'''
@ -181,4 +181,4 @@ applications dealing with uploads, there is also a Flask extension called
blacklisting of extensions and more.
.. _jQuery: https://jquery.com/
.. _Flask-Uploads: http://pythonhosted.org/Flask-Uploads/
.. _Flask-Uploads: https://pythonhosted.org/Flask-Uploads/

52
docs/patterns/packages.rst
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@ -8,15 +8,19 @@ module. That is quite simple. Imagine a small application looks like
this::
/yourapplication
/yourapplication.py
yourapplication.py
/static
/style.css
style.css
/templates
layout.html
index.html
login.html
...
If you find yourself stuck on something, feel free
to take a look at the source code for this example.
You'll find `the full src for this example here`_.
Simple Packages
---------------
@ -29,9 +33,9 @@ You should then end up with something like that::
/yourapplication
/yourapplication
/__init__.py
__init__.py
/static
/style.css
style.css
/templates
layout.html
index.html
@ -41,11 +45,36 @@ You should then end up with something like that::
But how do you run your application now? The naive ``python
yourapplication/__init__.py`` will not work. Let's just say that Python
does not want modules in packages to be the startup file. But that is not
a big problem, just add a new file called :file:`runserver.py` next to the inner
a big problem, just add a new file called :file:`setup.py` next to the inner
:file:`yourapplication` folder with the following contents::
from yourapplication import app
app.run(debug=True)
from setuptools import setup
setup(
name='yourapplication',
packages=['yourapplication'],
include_package_data=True,
install_requires=[
'flask',
],
)
In order to run the application you need to export an environment variable
that tells Flask where to find the application instance::
export FLASK_APP=yourapplication
If you are outside of the project directory make sure to provide the exact
path to your application directory. Similarly you can turn on "debug
mode" with this environment variable::
export FLASK_DEBUG=true
In order to install and run the application you need to issue the following
commands::
pip install -e .
flask run
What did we gain from this? Now we can restructure the application a bit
into multiple modules. The only thing you have to remember is the
@ -77,12 +106,12 @@ And this is what :file:`views.py` would look like::
You should then end up with something like that::
/yourapplication
/runserver.py
setup.py
/yourapplication
/__init__.py
/views.py
__init__.py
views.py
/static
/style.css
style.css
/templates
layout.html
index.html
@ -105,6 +134,7 @@ You should then end up with something like that::
.. _working-with-modules:
.. _the full src for this example here: https://github.com/pallets/flask/tree/master/examples/patterns/largerapp
Working with Blueprints
-----------------------

10
docs/patterns/sqlalchemy.rst
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@ -22,7 +22,7 @@ if you want to get started quickly.
You can download `Flask-SQLAlchemy`_ from `PyPI
<https://pypi.python.org/pypi/Flask-SQLAlchemy>`_.
.. _Flask-SQLAlchemy: http://pythonhosted.org/Flask-SQLAlchemy/
.. _Flask-SQLAlchemy: http://flask-sqlalchemy.pocoo.org/
Declarative
@ -108,9 +108,9 @@ Querying is simple as well:
>>> User.query.filter(User.name == 'admin').first()
<User u'admin'>
.. _SQLAlchemy: http://www.sqlalchemy.org/
.. _SQLAlchemy: https://www.sqlalchemy.org/
.. _declarative:
http://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/
https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/
Manual Object Relational Mapping
--------------------------------
@ -135,7 +135,7 @@ Here is an example :file:`database.py` module for your application::
def init_db():
metadata.create_all(bind=engine)
As for the declarative approach you need to close the session after
As in the declarative approach, you need to close the session after
each request or application context shutdown. Put this into your
application module::
@ -215,4 +215,4 @@ You can also pass strings of SQL statements to the
(1, u'admin', u'admin@localhost')
For more information about SQLAlchemy, head over to the
`website <http://www.sqlalchemy.org/>`_.
`website <https://www.sqlalchemy.org/>`_.

14
docs/patterns/sqlite3.rst
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@ -3,8 +3,8 @@
Using SQLite 3 with Flask
=========================
In Flask you can easily implement the opening of database connections on
demand and closing them when the context dies (usually at the end of the
In Flask you can easily implement the opening of database connections on
demand and closing them when the context dies (usually at the end of the
request).
Here is a simple example of how you can use SQLite 3 with Flask::
@ -71,7 +71,7 @@ Now in each request handling function you can access `g.db` to get the
current open database connection. To simplify working with SQLite, a
row factory function is useful. It is executed for every result returned
from the database to convert the result. For instance, in order to get
dictionaries instead of tuples, this could be inserted into the ``get_db``
dictionaries instead of tuples, this could be inserted into the ``get_db``
function we created above::
def make_dicts(cursor, row):
@ -102,15 +102,15 @@ This would use Row objects rather than dicts to return the results of queries. T
Additionally, it is a good idea to provide a query function that combines
getting the cursor, executing and fetching the results::
def query_db(query, args=(), one=False):
cur = get_db().execute(query, args)
rv = cur.fetchall()
cur.close()
return (rv[0] if rv else None) if one else rv
This handy little function, in combination with a row factory, makes
working with the database much more pleasant than it is by just using the
This handy little function, in combination with a row factory, makes
working with the database much more pleasant than it is by just using the
raw cursor and connection objects.
Here is how you can use it::
@ -131,7 +131,7 @@ To pass variable parts to the SQL statement, use a question mark in the
statement and pass in the arguments as a list. Never directly add them to
the SQL statement with string formatting because this makes it possible
to attack the application using `SQL Injections
<http://en.wikipedia.org/wiki/SQL_injection>`_.
<https://en.wikipedia.org/wiki/SQL_injection>`_.
Initial Schemas
---------------

2
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@ -19,7 +19,7 @@ forms.
fun. You can get it from `PyPI
<https://pypi.python.org/pypi/Flask-WTF>`_.
.. _Flask-WTF: http://pythonhosted.org/Flask-WTF/
.. _Flask-WTF: https://flask-wtf.readthedocs.io/en/stable/
The Forms
---------

281
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@ -50,7 +50,14 @@ to tell your terminal the application to work with by exporting the
$ flask run
* Running on http://127.0.0.1:5000/
If you are on Windows you need to use ``set`` instead of ``export``.
If you are on Windows, the environment variable syntax depends on command line
interpreter. On Command Prompt::
C:\path\to\app>set FLASK_APP=hello.py
And on PowerShell::
PS C:\path\to\app> $env:FLASK_APP = "hello.py"
Alternatively you can use :command:`python -m flask`::
@ -102,10 +109,10 @@ docs to see the alternative method for running a server.
Invalid Import Name
```````````````````
The ``-a`` argument to :command:`flask` is the name of the module to
import. In case that module is incorrectly named you will get an import
error upon start (or if debug is enabled when you navigate to the
application). It will tell you what it tried to import and why it failed.
The ``FLASK_APP`` environment variable is the name of the module to import at
:command:`flask run`. In case that module is incorrectly named you will get an
import error upon start (or if debug is enabled when you navigate to the
application). It will tell you what it tried to import and why it failed.
The most common reason is a typo or because you did not actually create an
``app`` object.
@ -153,20 +160,22 @@ Screenshot of the debugger in action:
:class: screenshot
:alt: screenshot of debugger in action
More information on using the debugger can be found in the `Werkzeug
documentation`_.
.. _Werkzeug documentation: http://werkzeug.pocoo.org/docs/debug/#using-the-debugger
Have another debugger in mind? See :ref:`working-with-debuggers`.
Routing
-------
Modern web applications have beautiful URLs. This helps people remember
the URLs, which is especially handy for applications that are used from
mobile devices with slower network connections. If the user can directly
go to the desired page without having to hit the index page it is more
likely they will like the page and come back next time.
Modern web applications use meaningful URLs to help users. Users are more
likely to like a page and come back if the page uses a meaningful URL they can
remember and use to directly visit a page.
As you have seen above, the :meth:`~flask.Flask.route` decorator is used to
bind a function to a URL. Here are some basic examples::
Use the :meth:`~flask.Flask.route` decorator to bind a function to a URL. ::
@app.route('/')
def index():
@ -176,16 +185,16 @@ bind a function to a URL. Here are some basic examples::
def hello():
return 'Hello, World'
But there is more to it! You can make certain parts of the URL dynamic and
attach multiple rules to a function.
You can do more! You can make parts of the URL dynamic and attach multiple
rules to a function.
Variable Rules
``````````````
To add variable parts to a URL you can mark these special sections as
``<variable_name>``. Such a part is then passed as a keyword argument to your
function. Optionally a converter can be used by specifying a rule with
``<converter:variable_name>``. Here are some nice examples::
You can add variable sections to a URL by marking sections with
``<variable_name>``. Your function then receives the ``<variable_name>``
as a keyword argument. Optionally, you can use a converter to specify the type
of the argument like ``<converter:variable_name>``. ::
@app.route('/user/<username>')
def show_user_profile(username):
@ -197,111 +206,111 @@ function. Optionally a converter can be used by specifying a rule with
# show the post with the given id, the id is an integer
return 'Post %d' % post_id
The following converters exist:
@app.route('/path/<path:subpath>')
def show_subpath(subpath):
# show the subpath after /path/
return 'Subpath %s' % subpath
=========== ===============================================
`string` accepts any text without a slash (the default)
`int` accepts integers
`float` like ``int`` but for floating point values
`path` like the default but also accepts slashes
`any` matches one of the items provided
`uuid` accepts UUID strings
=========== ===============================================
Converter types:
.. admonition:: Unique URLs / Redirection Behavior
========== ==========================================
``string`` (default) accepts any text without a slash
``int`` accepts positive integers
``float`` accepts positive floating point values
``path`` like ``string`` but also accepts slashes
``uuid`` accepts UUID strings
========== ==========================================
Flask's URL rules are based on Werkzeug's routing module. The idea
behind that module is to ensure beautiful and unique URLs based on
precedents laid down by Apache and earlier HTTP servers.
Unique URLs / Redirection Behavior
``````````````````````````````````
Take these two rules::
Take these two rules::
@app.route('/projects/')
def projects():
return 'The project page'
@app.route('/projects/')
def projects():
return 'The project page'
@app.route('/about')
def about():
return 'The about page'
@app.route('/about')
def about():
return 'The about page'
Though they look rather similar, they differ in their use of the trailing
slash in the URL *definition*. In the first case, the canonical URL for the
``projects`` endpoint has a trailing slash. In that sense, it is similar to
a folder on a filesystem. Accessing it without a trailing slash will cause
Flask to redirect to the canonical URL with the trailing slash.
Though they look similar, they differ in their use of the trailing slash in
the URL. In the first case, the canonical URL for the ``projects`` endpoint
uses a trailing slash. It's similar to a folder in a file system; if you
access the URL without a trailing slash, Flask redirects you to the
canonical URL with the trailing slash.
In the second case, however, the URL is defined without a trailing slash,
rather like the pathname of a file on UNIX-like systems. Accessing the URL
with a trailing slash will produce a 404 "Not Found" error.
This behavior allows relative URLs to continue working even if the trailing
slash is omitted, consistent with how Apache and other servers work. Also,
the URLs will stay unique, which helps search engines avoid indexing the
same page twice.
In the second case, however, the URL definition lacks a trailing slash,
like the pathname of a file on UNIX-like systems. Accessing the URL with a
trailing slash produces a 404 “Not Found” error.
This behavior allows relative URLs to continue working even if the trailing
slash is omitted, consistent with how Apache and other servers work. Also,
the URLs will stay unique, which helps search engines avoid indexing the
same page twice.
.. _url-building:
URL Building
````````````
If it can match URLs, can Flask also generate them? Of course it can. To
build a URL to a specific function you can use the :func:`~flask.url_for`
function. It accepts the name of the function as first argument and a number
of keyword arguments, each corresponding to the variable part of the URL rule.
Unknown variable parts are appended to the URL as query parameters. Here are
some examples::
To build a URL to a specific function, use the :func:`~flask.url_for` function.
It accepts the name of the function as its first argument and any number of
keyword arguments, each corresponding to a variable part of the URL rule.
Unknown variable parts are appended to the URL as query parameters.
Why would you want to build URLs using the URL reversing function
:func:`~flask.url_for` instead of hard-coding them into your templates?
1. Reversing is often more descriptive than hard-coding the URLs.
2. You can change your URLs in one go instead of needing to remember to
manually change hard-coded URLs.
3. URL building handles escaping of special characters and Unicode data
transparently.
4. If your application is placed outside the URL root, for example, in
``/myapplication`` instead of ``/``, :func:`~flask.url_for` properly
handles that for you.
For example, here we use the :meth:`~flask.Flask.test_request_context` method
to try out :func:`~flask.url_for`. :meth:`~flask.Flask.test_request_context`
tells Flask to behave as though it's handling a request even while we use a
Python shell. See :ref:`context-locals`. ::
from flask import Flask, url_for
app = Flask(__name__)
@app.route('/')
def index():
return 'index'
@app.route('/login')
def login():
return 'login'
@app.route('/user/<username>')
def profile(username):
return '{}'s profile'.format(username)
with app.test_request_context():
print(url_for('index'))
print(url_for('login'))
print(url_for('login', next='/'))
print(url_for('profile', username='John Doe'))
>>> from flask import Flask, url_for
>>> app = Flask(__name__)
>>> @app.route('/')
... def index(): pass
...
>>> @app.route('/login')
... def login(): pass
...
>>> @app.route('/user/<username>')
... def profile(username): pass
...
>>> with app.test_request_context():
... print url_for('index')
... print url_for('login')
... print url_for('login', next='/')
... print url_for('profile', username='John Doe')
...
/
/login
/login?next=/
/user/John%20Doe
(This also uses the :meth:`~flask.Flask.test_request_context` method, explained
below. It tells Flask to behave as though it is handling a request, even
though we are interacting with it through a Python shell. Have a look at the
explanation below. :ref:`context-locals`).
Why would you want to build URLs using the URL reversing function
:func:`~flask.url_for` instead of hard-coding them into your templates?
There are three good reasons for this:
1. Reversing is often more descriptive than hard-coding the URLs. More
importantly, it allows you to change URLs in one go, without having to
remember to change URLs all over the place.
2. URL building will handle escaping of special characters and Unicode
data transparently for you, so you don't have to deal with them.
3. If your application is placed outside the URL root - say, in
``/myapplication`` instead of ``/`` - :func:`~flask.url_for` will handle
that properly for you.
HTTP Methods
````````````
HTTP (the protocol web applications are speaking) knows different methods for
accessing URLs. By default, a route only answers to ``GET`` requests, but that
can be changed by providing the ``methods`` argument to the
:meth:`~flask.Flask.route` decorator. Here are some examples::
from flask import request
Web applications use different HTTP methods when accessing URLs. You should
familiarize yourself with the HTTP methods as you work with Flask. By default,
a route only answers to ``GET`` requests. You can use the ``methods`` argument
of the :meth:`~flask.Flask.route` decorator to handle different HTTP methods.
::
@app.route('/login', methods=['GET', 'POST'])
def login():
@ -310,64 +319,11 @@ can be changed by providing the ``methods`` argument to the
else:
show_the_login_form()
If ``GET`` is present, ``HEAD`` will be added automatically for you. You
don't have to deal with that. It will also make sure that ``HEAD`` requests
are handled as the `HTTP RFC`_ (the document describing the HTTP
protocol) demands, so you can completely ignore that part of the HTTP
specification. Likewise, as of Flask 0.6, ``OPTIONS`` is implemented for you
automatically as well.
If ``GET`` is present, Flask automatically adds support for the ``HEAD`` method
and handles ``HEAD`` requests according to the the `HTTP RFC`_. Likewise,
``OPTIONS`` is automatically implemented for you.
You have no idea what an HTTP method is? Worry not, here is a quick
introduction to HTTP methods and why they matter:
The HTTP method (also often called "the verb") tells the server what the
client wants to *do* with the requested page. The following methods are
very common:
``GET``
The browser tells the server to just *get* the information stored on
that page and send it. This is probably the most common method.
``HEAD``
The browser tells the server to get the information, but it is only
interested in the *headers*, not the content of the page. An
application is supposed to handle that as if a ``GET`` request was
received but to not deliver the actual content. In Flask you don't
have to deal with that at all, the underlying Werkzeug library handles
that for you.
``POST``
The browser tells the server that it wants to *post* some new
information to that URL and that the server must ensure the data is
stored and only stored once. This is how HTML forms usually
transmit data to the server.
``PUT``
Similar to ``POST`` but the server might trigger the store procedure
multiple times by overwriting the old values more than once. Now you
might be asking why this is useful, but there are some good reasons
to do it this way. Consider that the connection is lost during
transmission: in this situation a system between the browser and the
server might receive the request safely a second time without breaking
things. With ``POST`` that would not be possible because it must only
be triggered once.
``DELETE``
Remove the information at the given location.
``OPTIONS``
Provides a quick way for a client to figure out which methods are
supported by this URL. Starting with Flask 0.6, this is implemented
for you automatically.
Now the interesting part is that in HTML4 and XHTML1, the only methods a
form can submit to the server are ``GET`` and ``POST``. But with JavaScript
and future HTML standards you can use the other methods as well. Furthermore
HTTP has become quite popular lately and browsers are no longer the only
clients that are using HTTP. For instance, many revision control systems
use it.
.. _HTTP RFC: http://www.ietf.org/rfc/rfc2068.txt
.. _HTTP RFC: https://www.ietf.org/rfc/rfc2068.txt
Static Files
------------
@ -538,16 +494,16 @@ The Request Object
``````````````````
The request object is documented in the API section and we will not cover
it here in detail (see :class:`~flask.request`). Here is a broad overview of
it here in detail (see :class:`~flask.Request`). Here is a broad overview of
some of the most common operations. First of all you have to import it from
the ``flask`` module::
from flask import request
The current request method is available by using the
:attr:`~flask.request.method` attribute. To access form data (data
:attr:`~flask.Request.method` attribute. To access form data (data
transmitted in a ``POST`` or ``PUT`` request) you can use the
:attr:`~flask.request.form` attribute. Here is a full example of the two
:attr:`~flask.Request.form` attribute. Here is a full example of the two
attributes mentioned above::
@app.route('/login', methods=['POST', 'GET'])
@ -570,7 +526,7 @@ error page is shown instead. So for many situations you don't have to
deal with that problem.
To access parameters submitted in the URL (``?key=value``) you can use the
:attr:`~flask.request.args` attribute::
:attr:`~flask.Request.args` attribute::
searchword = request.args.get('key', '')
@ -579,7 +535,7 @@ We recommend accessing URL parameters with `get` or by catching the
bad request page in that case is not user friendly.
For a full list of methods and attributes of the request object, head over
to the :class:`~flask.request` documentation.
to the :class:`~flask.Request` documentation.
File Uploads
@ -817,6 +773,9 @@ values do not persist across requests, cookies are indeed enabled, and you are
not getting a clear error message, check the size of the cookie in your page
responses compared to the size supported by web browsers.
Besides the default client-side based sessions, if you want to handle
sessions on the server-side instead, there are several
Flask extensions that support this.
Message Flashing
----------------

15
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@ -119,9 +119,9 @@ understand what is actually happening. The new behavior is quite simple:
not executed yet or at all (for example in test environments sometimes
you might want to not execute before-request callbacks).
Now what happens on errors? In production mode if an exception is not
caught, the 500 internal server handler is called. In development mode
however the exception is not further processed and bubbles up to the WSGI
Now what happens on errors? If you are not in debug mode and an exception is not
caught, the 500 internal server handler is called. In debug mode
however the exception is not further processed and bubbles up to the WSGI
server. That way things like the interactive debugger can provide helpful
debug information.
@ -214,10 +214,11 @@ provide you with important information.
Starting with Flask 0.7 you have finer control over that behavior by
setting the ``PRESERVE_CONTEXT_ON_EXCEPTION`` configuration variable. By
default it's linked to the setting of ``DEBUG``. If the application is in
debug mode the context is preserved, in production mode it's not.
debug mode the context is preserved. If debug mode is set to off, the context
is not preserved.
Do not force activate ``PRESERVE_CONTEXT_ON_EXCEPTION`` in production mode
as it will cause your application to leak memory on exceptions. However
Do not force activate ``PRESERVE_CONTEXT_ON_EXCEPTION`` if debug mode is set to off
as it will cause your application to leak memory on exceptions. However,
it can be useful during development to get the same error preserving
behavior as in development mode when attempting to debug an error that
behavior as debug mode when attempting to debug an error that
only occurs under production settings.

104
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@ -15,7 +15,7 @@ it JavaScript) into the context of a website. To remedy this, developers
have to properly escape text so that it cannot include arbitrary HTML
tags. For more information on that have a look at the Wikipedia article
on `Cross-Site Scripting
<http://en.wikipedia.org/wiki/Cross-site_scripting>`_.
<https://en.wikipedia.org/wiki/Cross-site_scripting>`_.
Flask configures Jinja2 to automatically escape all values unless
explicitly told otherwise. This should rule out all XSS problems caused
@ -104,3 +104,105 @@ vulnerabilities
<https://github.com/pallets/flask/issues/248#issuecomment-59934857>`_, so
this behavior was changed and :func:`~flask.jsonify` now supports serializing
arrays.
Security Headers
----------------
Browsers recognize various response headers in order to control security. We
recommend reviewing each of the headers below for use in your application.
The `Flask-Talisman`_ extension can be used to manage HTTPS and the security
headers for you.
.. _Flask-Talisman: https://github.com/GoogleCloudPlatform/flask-talisman
HTTP Strict Transport Security (HSTS)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tells the browser to convert all HTTP requests to HTTPS, preventing
man-in-the-middle (MITM) attacks. ::
response.haders['Strict-Transport-Security'] = 'max-age=31536000; includeSubDomains'
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security
Content Security Policy (CSP)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tell the browser where it can load various types of resource from. This header
should be used whenever possible, but requires some work to define the correct
policy for your site. A very strict policy would be::
response.headers['Content-Security-Policy'] = "default-src: 'self'"
- https://csp.withgoogle.com/docs/index.html
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy
X-Content-Type-Options
~~~~~~~~~~~~~~~~~~~~~~
Forces the browser to honor the response content type instead of trying to
detect it, which can be abused to generate a cross-site scripting (XSS)
attack. ::
response.headers['X-Content-Type-Options'] = 'nosniff'
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
X-Frame-Options
~~~~~~~~~~~~~~~
Prevents external sites from embedding your site in an ``iframe``. This
prevents a class of attacks where clicks in the outer frame can be translated
invisibly to clicks on your page's elements. This is also known as
"clickjacking". ::
response.headers['X-Frame-Options'] = 'SAMEORIGIN'
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options
X-XSS-Protection
~~~~~~~~~~~~~~~~
The browser will try to prevent reflected XSS attacks by not loading the page
if the request contains something that looks like JavaScript and the response
contains the same data. ::
response.headers['X-XSS-Protection'] = '1; mode=block'
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-XSS-Protection
Set-Cookie options
~~~~~~~~~~~~~~~~~~
These options can be added to a ``Set-Cookie`` header to improve their
security. Flask has configuration options to set these on the session cookie.
They can be set on other cookies too.
- ``Secure`` limits cookies to HTTPS traffic only.
- ``HttpOnly`` protects the contents of cookies from being read with
JavaScript.
- ``SameSite`` ensures that cookies can only be requested from the same
domain that created them. It is not supported by Flask yet.
::
app.config.update(
SESSION_COOKIE_SECURE=True,
SESSION_COOKIE_HTTPONLY=True,
)
response.set_cookie('username', 'flask', secure=True, httponly=True)
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies#Secure_and_HttpOnly_cookies
HTTP Public Key Pinning (HPKP)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
This tells the browser to authenticate with the server using only the specific
certificate key to prevent MITM attacks.
.. warning::
Be careful when enabling this, as it is very difficult to undo if you set up
or upgrade your key incorrectly.
- https://developer.mozilla.org/en-US/docs/Web/HTTP/Public_Key_Pinning

4
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@ -27,7 +27,7 @@ executed in undefined order and do not modify any data.
The big advantage of signals over handlers is that you can safely
subscribe to them for just a split second. These temporary
subscriptions are helpful for unittesting for example. Say you want to
subscriptions are helpful for unit testing for example. Say you want to
know what templates were rendered as part of a request: signals allow you
to do exactly that.
@ -45,7 +45,7 @@ signal. When you subscribe to a signal, be sure to also provide a sender
unless you really want to listen for signals from all applications. This is
especially true if you are developing an extension.
For example, here is a helper context manager that can be used in a unittest
For example, here is a helper context manager that can be used in a unit test
to determine which templates were rendered and what variables were passed
to the template::

2
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@ -167,7 +167,7 @@ Docstring conventions:
"""
Module header:
The module header consists of an utf-8 encoding declaration (if non
The module header consists of a utf-8 encoding declaration (if non
ASCII letters are used, but it is recommended all the time) and a
standard docstring::

208
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@ -5,23 +5,30 @@ Testing Flask Applications
**Something that is untested is broken.**
The origin of this quote is unknown and while it is not entirely correct, it is also
not far from the truth. Untested applications make it hard to
The origin of this quote is unknown and while it is not entirely correct, it
is also not far from the truth. Untested applications make it hard to
improve existing code and developers of untested applications tend to
become pretty paranoid. If an application has automated tests, you can
safely make changes and instantly know if anything breaks.
Flask provides a way to test your application by exposing the Werkzeug
test :class:`~werkzeug.test.Client` and handling the context locals for you.
You can then use that with your favourite testing solution. In this documentation
we will use the :mod:`unittest` package that comes pre-installed with Python.
You can then use that with your favourite testing solution.
In this documentation we will use the `pytest`_ package as the base
framework for our tests. You can install it with ``pip``, like so::
pip install pytest
.. _pytest:
https://pytest.org
The Application
---------------
First, we need an application to test; we will use the application from
the :ref:`tutorial`. If you don't have that application yet, get the
sources from `the examples`_.
source code from `the examples`_.
.. _the examples:
https://github.com/pallets/flask/tree/master/examples/flaskr/
@ -29,90 +36,91 @@ sources from `the examples`_.
The Testing Skeleton
--------------------
In order to test the application, we add a second module
(:file:`flaskr_tests.py`) and create a unittest skeleton there::
We begin by adding a tests directory under the application root. Then
create a Python file to store our tests (:file:`test_flaskr.py`). When we
format the filename like ``test_*.py``, it will be auto-discoverable by
pytest.
Next, we create a `pytest fixture`_ called
:func:`client` that configures
the application for testing and initializes a new database.::
import os
import flaskr
import unittest
import tempfile
class FlaskrTestCase(unittest.TestCase):
import pytest
def setUp(self):
self.db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
flaskr.app.config['TESTING'] = True
self.app = flaskr.app.test_client()
with flaskr.app.app_context():
flaskr.init_db()
from flaskr import flaskr
def tearDown(self):
os.close(self.db_fd)
os.unlink(flaskr.app.config['DATABASE'])
if __name__ == '__main__':
unittest.main()
@pytest.fixture
def client():
db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
flaskr.app.config['TESTING'] = True
client = flaskr.app.test_client()
The code in the :meth:`~unittest.TestCase.setUp` method creates a new test
client and initializes a new database. This function is called before
each individual test function is run. To delete the database after the
test, we close the file and remove it from the filesystem in the
:meth:`~unittest.TestCase.tearDown` method. Additionally during setup the
``TESTING`` config flag is activated. What it does is disable the error
catching during request handling so that you get better error reports when
performing test requests against the application.
with flaskr.app.app_context():
flaskr.init_db()
This test client will give us a simple interface to the application. We can
trigger test requests to the application, and the client will also keep track
of cookies for us.
yield client
Because SQLite3 is filesystem-based we can easily use the tempfile module
os.close(db_fd)
os.unlink(flaskr.app.config['DATABASE'])
This client fixture will be called by each individual test. It gives us a
simple interface to the application, where we can trigger test requests to the
application. The client will also keep track of cookies for us.
During setup, the ``TESTING`` config flag is activated. What
this does is disable error catching during request handling, so that
you get better error reports when performing test requests against the
application.
Because SQLite3 is filesystem-based, we can easily use the :mod:`tempfile` module
to create a temporary database and initialize it. The
:func:`~tempfile.mkstemp` function does two things for us: it returns a
low-level file handle and a random file name, the latter we use as
database name. We just have to keep the `db_fd` around so that we can use
the :func:`os.close` function to close the file.
To delete the database after the test, the fixture closes the file and removes
it from the filesystem.
If we now run the test suite, we should see the following output::
$ python flaskr_tests.py
$ pytest
----------------------------------------------------------------------
Ran 0 tests in 0.000s
================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 0 items
OK
=========== no tests ran in 0.07 seconds ============
Even though it did not run any actual tests, we already know that our flaskr
Even though it did not run any actual tests, we already know that our ``flaskr``
application is syntactically valid, otherwise the import would have died
with an exception.
.. _pytest fixture:
https://docs.pytest.org/en/latest/fixture.html
The First Test
--------------
Now it's time to start testing the functionality of the application.
Let's check that the application shows "No entries here so far" if we
access the root of the application (``/``). To do this, we add a new
test method to our class, like this::
access the root of the application (``/``). To do this, we add a new
test function to :file:`test_flaskr.py`, like this::
class FlaskrTestCase(unittest.TestCase):
def test_empty_db(client):
"""Start with a blank database."""
def setUp(self):
self.db_fd, flaskr.app.config['DATABASE'] = tempfile.mkstemp()
self.app = flaskr.app.test_client()
flaskr.init_db()
def tearDown(self):
os.close(self.db_fd)
os.unlink(flaskr.app.config['DATABASE'])
def test_empty_db(self):
rv = self.app.get('/')
assert b'No entries here so far' in rv.data
rv = client.get('/')
assert b'No entries here so far' in rv.data
Notice that our test functions begin with the word `test`; this allows
:mod:`unittest` to automatically identify the method as a test to run.
`pytest`_ to automatically identify the function as a test to run.
By using `self.app.get` we can send an HTTP ``GET`` request to the application with
By using ``client.get`` we can send an HTTP ``GET`` request to the application with
the given path. The return value will be a :class:`~flask.Flask.response_class` object.
We can now use the :attr:`~werkzeug.wrappers.BaseResponse.data` attribute to inspect
the return value (as string) from the application. In this case, we ensure that
@ -120,12 +128,15 @@ the return value (as string) from the application. In this case, we ensure that
Run it again and you should see one passing test::
$ python flaskr_tests.py
.
----------------------------------------------------------------------
Ran 1 test in 0.034s
$ pytest -v
OK
================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 1 items
tests/test_flaskr.py::test_empty_db PASSED
============= 1 passed in 0.10 seconds ==============
Logging In and Out
------------------
@ -136,67 +147,78 @@ of the application. To do this, we fire some requests to the login and logout
pages with the required form data (username and password). And because the
login and logout pages redirect, we tell the client to `follow_redirects`.
Add the following two methods to your `FlaskrTestCase` class::
Add the following two functions to your :file:`test_flaskr.py` file::
def login(self, username, password):
return self.app.post('/login', data=dict(
username=username,
password=password
), follow_redirects=True)
def login(client, username, password):
return client.post('/login', data=dict(
username=username,
password=password
), follow_redirects=True)
def logout(self):
return self.app.get('/logout', follow_redirects=True)
def logout(client):
return client.get('/logout', follow_redirects=True)
Now we can easily test that logging in and out works and that it fails with
invalid credentials. Add this new test to the class::
invalid credentials. Add this new test function::
def test_login_logout(self):
rv = self.login('admin', 'default')
assert 'You were logged in' in rv.data
rv = self.logout()
assert 'You were logged out' in rv.data
rv = self.login('adminx', 'default')
assert 'Invalid username' in rv.data
rv = self.login('admin', 'defaultx')
assert 'Invalid password' in rv.data
def test_login_logout(client):
"""Make sure login and logout works."""
rv = login(client, flaskr.app.config['USERNAME'], flaskr.app.config['PASSWORD'])
assert b'You were logged in' in rv.data
rv = logout(client)
assert b'You were logged out' in rv.data
rv = login(client, flaskr.app.config['USERNAME'] + 'x', flaskr.app.config['PASSWORD'])
assert b'Invalid username' in rv.data
rv = login(client, flaskr.app.config['USERNAME'], flaskr.app.config['PASSWORD'] + 'x')
assert b'Invalid password' in rv.data
Test Adding Messages
--------------------
We should also test that adding messages works. Add a new test method
We should also test that adding messages works. Add a new test function
like this::
def test_messages(self):
self.login('admin', 'default')
rv = self.app.post('/add', data=dict(
def test_messages(client):
"""Test that messages work."""
login(client, flaskr.app.config['USERNAME'], flaskr.app.config['PASSWORD'])
rv = client.post('/add', data=dict(
title='<Hello>',
text='<strong>HTML</strong> allowed here'
), follow_redirects=True)
assert 'No entries here so far' not in rv.data
assert '&lt;Hello&gt;' in rv.data
assert '<strong>HTML</strong> allowed here' in rv.data
assert b'No entries here so far' not in rv.data
assert b'&lt;Hello&gt;' in rv.data
assert b'<strong>HTML</strong> allowed here' in rv.data
Here we check that HTML is allowed in the text but not in the title,
which is the intended behavior.
Running that should now give us three passing tests::
$ python flaskr_tests.py
...
----------------------------------------------------------------------
Ran 3 tests in 0.332s
$ pytest -v
OK
================ test session starts ================
rootdir: ./flask/examples/flaskr, inifile: setup.cfg
collected 3 items
tests/test_flaskr.py::test_empty_db PASSED
tests/test_flaskr.py::test_login_logout PASSED
tests/test_flaskr.py::test_messages PASSED
============= 3 passed in 0.23 seconds ==============
For more complex tests with headers and status codes, check out the
`MiniTwit Example`_ from the sources which contains a larger test
suite.
.. _MiniTwit Example:
https://github.com/pallets/flask/tree/master/examples/minitwit/
Other Testing Tricks
--------------------
@ -208,7 +230,7 @@ temporarily. With this you can access the :class:`~flask.request`,
functions. Here is a full example that demonstrates this approach::
import flask
app = flask.Flask(__name__)
with app.test_request_context('/?name=Peter'):

2
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@ -1,6 +1,6 @@
.. _tutorial-css:
Step 9: Adding Style
Step 8: Adding Style
====================
Now that everything else works, it's time to add some style to the

5
docs/tutorial/dbcon.rst
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@ -3,7 +3,10 @@
Step 4: Database Connections
----------------------------
You now have a function for establishing a database connection with
Let's continue building our code in the ``flaskr.py`` file.
(Scroll to the end of the page for more about project layout.)
You currently have a function for establishing a database connection with
`connect_db`, but by itself, it is not particularly useful. Creating and
closing database connections all the time is very inefficient, so you will
need to keep it around for longer. Because database connections

33
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@ -9,33 +9,39 @@ systems need a schema that tells them how to store that information.
Before starting the server for the first time, it's important to create
that schema.
Such a schema can be created by piping the ``schema.sql`` file into the
`sqlite3` command as follows::
Such a schema could be created by piping the ``schema.sql`` file into the
``sqlite3`` command as follows::
sqlite3 /tmp/flaskr.db < schema.sql
The downside of this is that it requires the ``sqlite3`` command to be
installed, which is not necessarily the case on every system. This also
requires that you provide the path to the database, which can introduce
errors. It's a good idea to add a function that initializes the database
for you, to the application.
However, the downside of this is that it requires the ``sqlite3`` command
to be installed, which is not necessarily the case on every system. This
also requires that you provide the path to the database, which can introduce
errors.
To do this, you can create a function and hook it into a :command:`flask`
command that initializes the database. For now just take a look at the
code segment below. A good place to add this function, and command, is
just below the `connect_db` function in :file:`flaskr.py`::
Instead of the ``sqlite3`` command above, it's a good idea to add a function
to our application that initializes the database for you. To do this, you
can create a function and hook it into a :command:`flask` command that
initializes the database.
Take a look at the code segment below. A good place to add this function,
and command, is just below the ``connect_db`` function in :file:`flaskr.py`::
def init_db():
db = get_db()
with app.open_resource('schema.sql', mode='r') as f:
db.cursor().executescript(f.read())
db.commit()
@app.cli.command('initdb')
def initdb_command():
"""Initializes the database."""
init_db()
print 'Initialized the database.'
print('Initialized the database.')
The ``app.cli.command()`` decorator registers a new command with the
:command:`flask` script. When the command executes, Flask will automatically
@ -59,7 +65,8 @@ On that cursor, there is a method to execute a complete script. Finally, you
only have to commit the changes. SQLite3 and other transactional
databases will not commit unless you explicitly tell it to.
Now, it is possible to create a database with the :command:`flask` script::
Now, in a terminal, from the application root directory :file:`flaskr/` it is
possible to create a database with the :command:`flask` script::
flask initdb
Initialized the database.

16
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@ -3,8 +3,11 @@
Step 0: Creating The Folders
============================
Before getting started, you will need to create the folders needed for this
application::
It is recommended to install your Flask application within a virtualenv. Please
read the :ref:`installation` section to set up your environment.
Now that you have installed Flask, you will need to create the folders required
for this tutorial. Your directory structure will look like this::
/flaskr
/flaskr
@ -13,13 +16,14 @@ application::
The application will be installed and run as Python package. This is the
recommended way to install and run Flask applications. You will see exactly
how to run ``flaskr`` later on in this tutorial. For now go ahead and create
the applications directory structure. In the next few steps you will be
creating the database schema as well as the main module.
how to run ``flaskr`` later on in this tutorial.
For now go ahead and create the applications directory structure. In the next
few steps you will be creating the database schema as well as the main module.
As a quick side note, the files inside of the :file:`static` folder are
available to users of the application via HTTP. This is the place where CSS and
Javascript files go. Inside the :file:`templates` folder, Flask will look for
JavaScript files go. Inside the :file:`templates` folder, Flask will look for
`Jinja2`_ templates. You will see examples of this later on.
For now you should continue with :ref:`tutorial-schema`.

20
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@ -3,19 +3,19 @@
Tutorial
========
You want to develop an application with Python and Flask? Here you have
the chance to learn by example. In this tutorial, we will create a simple
microblogging application. It only supports one user that can create
text-only entries and there are no feeds or comments, but it still
features everything you need to get started. We will use Flask and SQLite
as a database (which comes out of the box with Python) so there is nothing
else you need.
Learn by example to develop an application with Python and Flask.
In this tutorial, we will create a simple blogging application. It only
supports one user, only allows text entries, and has no feeds or comments.
While very simple, this example still features everything you need to get
started. In addition to Flask, we will use SQLite for the database, which is
built-in to Python, so there is nothing else you need.
If you want the full source code in advance or for comparison, check out
the `example source`_.
.. _example source:
https://github.com/pallets/flask/tree/master/examples/flaskr/
.. _example source: https://github.com/pallets/flask/tree/master/examples/flaskr/
.. toctree::
:maxdepth: 2
@ -24,7 +24,7 @@ the `example source`_.
folders
schema
setup
setuptools
packaging
dbcon
dbinit
views

4
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@ -22,7 +22,7 @@ connections in a more intelligent way, allowing you to target different
relational databases at once and more. You might also want to consider
one of the popular NoSQL databases if your data is more suited for those.
Here a screenshot of the final application:
Here is a screenshot of the final application:
.. image:: ../_static/flaskr.png
:align: center
@ -31,4 +31,4 @@ Here a screenshot of the final application:
Continue with :ref:`tutorial-folders`.
.. _SQLAlchemy: http://www.sqlalchemy.org/
.. _SQLAlchemy: https://www.sqlalchemy.org/

63
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@ -1,7 +1,7 @@
.. _tutorial-setuptools:
.. _tutorial-packaging:
Step 3: Installing flaskr with setuptools
=========================================
Step 3: Installing flaskr as a Package
======================================
Flask is now shipped with built-in support for `Click`_. Click provides
Flask with enhanced and extensible command line utilities. Later in this
@ -9,21 +9,23 @@ tutorial you will see exactly how to extend the ``flask`` command line
interface (CLI).
A useful pattern to manage a Flask application is to install your app
using `setuptools`_. This involves creating a :file:`setup.py`
in the projects root directory. You also need to add an empty
:file:`__init__.py` file to make the :file:`flaskr/flaskr` directory
a package. The code structure at this point should be::
following the `Python Packaging Guide`_. Presently this involves
creating two new files; :file:`setup.py` and :file:`MANIFEST.in` in the
projects root directory. You also need to add an :file:`__init__.py`
file to make the :file:`flaskr/flaskr` directory a package. After these
changes, your code structure should be::
/flaskr
/flaskr
__init__.py
/static
/templates
flaskr.py
schema.sql
setup.py
MANIFEST.in
The content of the ``setup.py`` file for ``flaskr`` is:
.. sourcecode:: python
Create the ``setup.py`` file for ``flaskr`` with the following content::
from setuptools import setup
@ -39,38 +41,53 @@ The content of the ``setup.py`` file for ``flaskr`` is:
When using setuptools, it is also necessary to specify any special files
that should be included in your package (in the :file:`MANIFEST.in`).
In this case, the static and templates directories need to be included,
as well as the schema. Create the :file:`MANIFEST.in` and add the
following lines::
as well as the schema.
Create the :file:`MANIFEST.in` and add the following lines::
graft flaskr/templates
graft flaskr/static
include flaskr/schema.sql
Next, to simplify locating the application, create the file,
:file:`flaskr/__init__.py` containing only the following import statement::
from .flaskr import app
This import statement brings the application instance into the top-level
of the application package. When it is time to run the application, the
Flask development server needs the location of the app instance. This
import statement simplifies the location process. Without the above
import statement, the export statement a few steps below would need to be
``export FLASK_APP=flaskr.flaskr``.
At this point you should be able to install the application. As usual, it
is recommended to install your Flask application within a `virtualenv`_.
With that said, go ahead and install the application with::
With that said, from the ``flaskr/`` directory, go ahead and install the
application with::
pip install --editable .
.. note:: The above installation command assumes that it is run within the
projects root directory, `flaskr/`. Also, the `editable` flag allows
editing source code without having to reinstall the Flask app each time
you make changes.
The above installation command assumes that it is run within the projects
root directory, ``flaskr/``. The ``editable`` flag allows editing
source code without having to reinstall the Flask app each time you make
changes. The flaskr app is now installed in your virtualenv (see output
of ``pip freeze``).
With that out of the way, you should be able to start up the application.
Do this with the following commands::
Do this on Mac or Linux with the following commands in ``flaskr/``::
export FLASK_APP=flaskr.flaskr
export FLASK_DEBUG=1
export FLASK_APP=flaskr
export FLASK_DEBUG=true
flask run
(In case you are on Windows you need to use `set` instead of `export`).
(In case you are on Windows you need to use ``set`` instead of ``export``).
The :envvar:`FLASK_DEBUG` flag enables or disables the interactive debugger.
*Never leave debug mode activated in a production system*, because it will
allow users to execute code on the server!
You will see a message telling you that server has started along with
the address at which you can access it.
the address at which you can access it in a browser.
When you head over to the server in your browser, you will get a 404 error
because we don't have any views yet. That will be addressed a little later,
@ -85,5 +102,5 @@ but first, you should get the database working.
Continue with :ref:`tutorial-dbcon`.
.. _Click: http://click.pocoo.org
.. _setuptools: https://setuptools.readthedocs.io
.. _Python Packaging Guide: https://packaging.python.org
.. _virtualenv: https://virtualenv.pypa.io

68
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@ -3,27 +3,31 @@
Step 2: Application Setup Code
==============================
Now that the schema is in place, you can create the application module,
:file:`flaskr.py`. This file should be placed inside of the
:file:`flaskr/flaskr` folder. The first several lines of code in the
application module are the needed import statements. After that there will be a
few lines of configuration code. For small applications like ``flaskr``, it is
possible to drop the configuration directly into the module. However, a cleaner
solution is to create a separate ``.ini`` or ``.py`` file, load that, and
import the values from there.
Next, we will create the application module, :file:`flaskr.py`. Just like the
:file:`schema.sql` file you created in the previous step, this file should be
placed inside of the :file:`flaskr/flaskr` folder.
For this tutorial, all the Python code we use will be put into this file
(except for one line in ``__init__.py``, and any testing or optional files you
decide to create).
The first several lines of code in the application module are the needed import
statements. After that there will be a few lines of configuration code.
For small applications like ``flaskr``, it is possible to drop the configuration
directly into the module. However, a cleaner solution is to create a separate
``.py`` file, load that, and import the values from there.
Here are the import statements (in :file:`flaskr.py`)::
# all the imports
import os
import sqlite3
from flask import Flask, request, session, g, redirect, url_for, abort, \
render_template, flash
from flask import (Flask, request, session, g, redirect, url_for, abort,
render_template, flash)
The next couple lines will create the actual application instance and
initialize it with the config from the same file in :file:`flaskr.py`:
.. sourcecode:: python
initialize it with the config from the same file in :file:`flaskr.py`::
app = Flask(__name__) # create the application instance :)
app.config.from_object(__name__) # load config from this file , flaskr.py
@ -37,8 +41,8 @@ initialize it with the config from the same file in :file:`flaskr.py`:
))
app.config.from_envvar('FLASKR_SETTINGS', silent=True)
The :class:`~flask.Config` object works similarly to a dictionary, so it can be
updated with new values.
In the above code, the :class:`~flask.Config` object works similarly to a
dictionary, so it can be updated with new values.
.. admonition:: Database Path
@ -58,15 +62,15 @@ updated with new values.
Usually, it is a good idea to load a separate, environment-specific
configuration file. Flask allows you to import multiple configurations and it
will use the setting defined in the last import. This enables robust
configuration setups. :meth:`~flask.Config.from_envvar` can help achieve this.
.. sourcecode:: python
configuration setups. :meth:`~flask.Config.from_envvar` can help achieve
this. ::
app.config.from_envvar('FLASKR_SETTINGS', silent=True)
Simply define the environment variable :envvar:`FLASKR_SETTINGS` that points to
a config file to be loaded. The silent switch just tells Flask to not complain
if no such environment key is set.
If you want to do this (not required for this tutorial) simply define the
environment variable :envvar:`FLASKR_SETTINGS` that points to a config file
to be loaded. The silent switch just tells Flask to not complain if no such
environment key is set.
In addition to that, you can use the :meth:`~flask.Config.from_object`
method on the config object and provide it with an import name of a
@ -76,22 +80,22 @@ that in all cases, only variable names that are uppercase are considered.
The ``SECRET_KEY`` is needed to keep the client-side sessions secure.
Choose that key wisely and as hard to guess and complex as possible.
Lastly, you will add a method that allows for easy connections to the
specified database. This can be used to open a connection on request and
also from the interactive Python shell or a script. This will come in
handy later. You can create a simple database connection through SQLite and
then tell it to use the :class:`sqlite3.Row` object to represent rows.
This allows the rows to be treated as if they were dictionaries instead of
tuples.
.. sourcecode:: python
Lastly, add a method that allows for easy connections to the specified
database. ::
def connect_db():
"""Connects to the specific database."""
rv = sqlite3.connect(app.config['DATABASE'])
rv.row_factory = sqlite3.Row
return rv
This can be used to open a connection on request and also from the
interactive Python shell or a script. This will come in handy later.
You can create a simple database connection through SQLite and then tell
it to use the :class:`sqlite3.Row` object to represent rows. This allows
the rows to be treated as if they were dictionaries instead of tuples.
In the next section you will see how to run the application.
Continue with :ref:`tutorial-setuptools`.
Continue with :ref:`tutorial-packaging`.

11
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@ -1,6 +1,6 @@
.. _tutorial-templates:
Step 8: The Templates
Step 7: The Templates
=====================
Now it is time to start working on the templates. As you may have
@ -15,7 +15,8 @@ escaped with their XML equivalents.
We are also using template inheritance which makes it possible to reuse
the layout of the website in all pages.
Put the following templates into the :file:`templates` folder:
Create the follwing three HTML files and place them in the
:file:`templates` folder:
.. _Jinja2: http://jinja.pocoo.org/docs/templates
@ -59,7 +60,7 @@ show_entries.html
This template extends the :file:`layout.html` template from above to display the
messages. Note that the ``for`` loop iterates over the messages we passed
in with the :func:`~flask.render_template` function. Notice that the form is
configured to to submit to the `add_entry` view function and use ``POST`` as
configured to submit to the `add_entry` view function and use ``POST`` as
HTTP method:
.. sourcecode:: html+jinja
@ -79,9 +80,9 @@ HTTP method:
{% endif %}
<ul class=entries>
{% for entry in entries %}
<li><h2>{{ entry.title }}</h2>{{ entry.text|safe }}
<li><h2>{{ entry.title }}</h2>{{ entry.text|safe }}</li>
{% else %}
<li><em>Unbelievable. No entries here so far</em>
<li><em>Unbelievable. No entries here so far</em></li>
{% endfor %}
</ul>
{% endblock %}

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@ -9,10 +9,10 @@ modifications in the future. The application above is used as a basic
example of how to perform unit testing in the :ref:`testing` section of the
documentation. Go there to see how easy it is to test Flask applications.
Adding Tests to flaskr
======================
Adding tests to flaskr
----------------------
Assuming you have seen the testing section above and have either written
Assuming you have seen the :ref:`testing` section and have either written
your own tests for ``flaskr`` or have followed along with the examples
provided, you might be wondering about ways to organize the project.
@ -24,30 +24,38 @@ One possible and recommended project structure is::
static/
templates/
tests/
context.py
test_flaskr.py
setup.py
MANIFEST.in
For now go ahead a create the :file:`tests/` directory as well as the
:file:`context.py` and :file:`test_flaskr.py` files, if you haven't
already. The context file is used as an import helper. The contents
of that file are::
For now go ahead a create the :file:`tests/` directory as well as the
:file:`test_flaskr.py` file.
import sys, os
Running the tests
-----------------
basedir = os.path.dirname(os.path.abspath(__file__))
sys.path.insert(0, basedir + '/../')
At this point you can run the tests. Here ``pytest`` will be used.
from flaskr import flaskr
.. note:: Make sure that ``pytest`` is installed in the same virtualenv
as flaskr. Otherwise ``pytest`` test will not be able to import the
required components to test the application::
Testing + Setuptools
====================
pip install -e .
pip install pytest
One way to handle testing is to integrate it with ``setuptools``. All it
requires is adding a couple of lines to the :file:`setup.py` file and
creating a new file :file:`setup.cfg`. Go ahead and update the
:file:`setup.py` to contain::
Run and watch the tests pass, within the top-level :file:`flaskr/`
directory as::
pytest
Testing + setuptools
--------------------
One way to handle testing is to integrate it with ``setuptools``. Here
that requires adding a couple of lines to the :file:`setup.py` file and
creating a new file :file:`setup.cfg`. One benefit of running the tests
this way is that you do not have to install ``pytest``. Go ahead and
update the :file:`setup.py` file to contain::
from setuptools import setup
@ -58,7 +66,6 @@ creating a new file :file:`setup.cfg`. Go ahead and update the
install_requires=[
'flask',
],
)
setup_requires=[
'pytest-runner',
],
@ -66,6 +73,7 @@ creating a new file :file:`setup.cfg`. Go ahead and update the
'pytest',
],
)
Now create :file:`setup.cfg` in the project root (alongside
:file:`setup.py`)::
@ -85,4 +93,4 @@ found, run, and hopefully pass.
This is one possible way to run and manage testing. Here ``pytest`` is
used, but there are other options such as ``nose``. Integrating testing
with ``setuptools`` is convenient because it is not necessary to actually
download ``pytest`` or any other testing framework one might use.
download ``pytest`` or any other testing framework one might use.

5
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@ -1,10 +1,11 @@
.. _tutorial-views:
Step 7: The View Functions
Step 6: The View Functions
==========================
Now that the database connections are working, you can start writing the
view functions. You will need four of them:
view functions. You will need four of them; Show Entries, Add New Entry,
Login and Logout. Add the following code snipets to :file:`flaskr.py`.
Show Entries
------------

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@ -19,7 +19,45 @@ providing the ``--upgrade`` parameter::
$ pip install --upgrade Flask
.. _upgrading-to-10:
.. _upgrading-to-012:
Version 0.12
------------
Changes to send_file
````````````````````
The ``filename`` is no longer automatically inferred from file-like objects.
This means that the following code will no longer automatically have
``X-Sendfile`` support, etag generation or MIME-type guessing::
response = send_file(open('/path/to/file.txt'))
Any of the following is functionally equivalent::
fname = '/path/to/file.txt'
# Just pass the filepath directly
response = send_file(fname)
# Set the MIME-type and ETag explicitly
response = send_file(open(fname), mimetype='text/plain')
response.set_etag(...)
# Set `attachment_filename` for MIME-type guessing
# ETag still needs to be manually set
response = send_file(open(fname), attachment_filename=fname)
response.set_etag(...)
The reason for this is that some file-like objects have an invalid or even
misleading ``name`` attribute. Silently swallowing errors in such cases was not
a satisfying solution.
Additionally the default of falling back to ``application/octet-stream`` has
been restricted. If Flask can't guess one or the user didn't provide one, the
function fails if no filename information was provided.
.. _upgrading-to-011:
Version 0.11
------------
@ -105,7 +143,7 @@ when there is no request context yet but an application context. The old
``flask.Flask.request_globals_class`` attribute was renamed to
:attr:`flask.Flask.app_ctx_globals_class`.
.. _Flask-OldSessions: http://pythonhosted.org/Flask-OldSessions/
.. _Flask-OldSessions: https://pythonhosted.org/Flask-OldSessions/
Version 0.9
-----------
@ -160,7 +198,7 @@ applications with Flask. Because we want to make upgrading as easy as
possible we tried to counter the problems arising from these changes by
providing a script that can ease the transition.
The script scans your whole application and generates an unified diff with
The script scans your whole application and generates a unified diff with
changes it assumes are safe to apply. However as this is an automated
tool it won't be able to find all use cases and it might miss some. We
internally spread a lot of deprecation warnings all over the place to make