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Explained Flask constructor better. This fixes #70

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Armin Ronacher 2010-07-01 12:56:34 +02:00
parent bc662a546e
commit 3ab318a7dd
2 changed files with 34 additions and 1 deletions
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7
docs/quickstart.rst
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@ -38,7 +38,12 @@ see your hello world greeting.
So what did that code do? So what did that code do?
1. first we imported the :class:`~flask.Flask` class. An instance of this 1. first we imported the :class:`~flask.Flask` class. An instance of this
class will be our WSGI application. class will be our WSGI application. The first argument is the name of
the application's module. If you are using a single module (like here)
you should use `__name__` because depending on if it's started as
application or imported as module the name will be different
(``'__main__'`` versus the actual import name). For more information
on that, have a look at the :class:`~flask.Flask` documentation.
2. next we create an instance of it. We pass it the name of the module / 2. next we create an instance of it. We pass it the name of the module /
package. This is needed so that Flask knows where it should look for package. This is needed so that Flask knows where it should look for
templates, static files and so on. templates, static files and so on.

28
flask.py
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@ -806,6 +806,34 @@ class Flask(_PackageBoundObject):
from flask import Flask from flask import Flask
app = Flask(__name__) app = Flask(__name__)
.. admonition:: About the First Parameter
The idea of the first parameter is to give Flask an idea what
belongs to your application. This name is used to find resources
on the file system, can be used by extensions to improve debugging
information and a lot more.
So it's important what you provide there. If you are using a single
module, `__name__` is always the correct value. If you however are
using a package, it's usually recommended to hardcode the name of
your package there.
For example if your application is defined in `yourapplication/app.py`
you should create it with one of the two versions below::
app = Flask('yourapplication')
app = Flask(__name__.split('.')[0])
Why is that? The application will work even with `__name__`, thanks
to how resources are looked up. However it will make debugging more
painful. Certain extensions can make assumptions based on the
import name of your application. For example the Flask-SQLAlchemy
extension will look for the code in your application that triggered
an SQL query in debug mode. If the import name is not properly set
up, that debugging information is lost. (For example it would only
pick up SQL queries in `yourapplicaiton.app` and not
`yourapplication.views.frontend`)
""" """
#: The class that is used for request objects. See :class:`~flask.Request` #: The class that is used for request objects. See :class:`~flask.Request`