forked from orbit-oss/flask
Updated docs for click support
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4 changed files with 127 additions and 28 deletions
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@ -23,6 +23,8 @@ instructions for web development with Flask.
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reqcontext
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blueprints
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extensions
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cli
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server
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shell
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patterns/index
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deploying/index
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@ -20,16 +20,19 @@ A minimal Flask application looks something like this::
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def hello_world():
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return 'Hello World!'
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if __name__ == '__main__':
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app.run()
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Just save it as `hello.py` (or something similar) and run it with your Python
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interpreter. Make sure to not call your application `flask.py` because this
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would conflict with Flask itself.
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::
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To run the application you can either use the ``flask`` command or
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python's ``-m`` switch with Flask::
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$ python hello.py
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$ flask -a hello run
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* Running on http://127.0.0.1:5000/
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or alternatively::
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$ python -m flask -a hello run
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* Running on http://127.0.0.1:5000/
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Now head over to `http://127.0.0.1:5000/ <http://127.0.0.1:5000/>`_, and you
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@ -51,10 +54,8 @@ So what did that code do?
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4. The function is given a name which is also used to generate URLs for that
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particular function, and returns the message we want to display in the
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user's browser.
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5. Finally we use the :meth:`~flask.Flask.run` function to run the local server
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with our application. The ``if __name__ == '__main__':`` makes sure the
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server only runs if the script is executed directly from the Python
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interpreter and not used as an imported module.
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5. Finally we use the Flask development server to run the local server
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with our application.
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To stop the server, hit control-C.
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@ -67,37 +68,73 @@ To stop the server, hit control-C.
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default because in debugging mode a user of the application can execute
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arbitrary Python code on your computer.
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If you have `debug` disabled or trust the users on your network, you can
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make the server publicly available simply by changing the call of the
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:meth:`~flask.Flask.run` method to look like this::
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If you have the debugger disabled or trust the users on your network,
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you can make the server publicly available simply by adding
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``--host=0.0.0.0`` to the command line::
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app.run(host='0.0.0.0')
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flask -a hello run --host=0.0.0.0
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This tells your operating system to listen on all public IPs.
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What to do if the Server does not Start
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---------------------------------------
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In case the ``python -m flask`` fails or ``flask`` does not exist,
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there are multiple reasons this might be the case. First of all you need
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to look at the error message.
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Old Version of Flask
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````````````````````
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Versions of Flask older than 1.0 use to have different ways to start the
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application. In short, the ``flask`` command did not exist, and
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neither did ``python -m flask``. In that case you have two options:
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either upgrade to newer Flask versions or have a look at the :ref:`server`
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docs to see the alternative method for running a server.
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Python older 2.7
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````````````````
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In case you have a version of Python older than 2.7 ``python -m flask``
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does not work. You can either use ``flask`` or ``python -m
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flask.cli`` as an alternative. This is because Python before 2.7 does no
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permit packages to act as executable modules. For more information see
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:ref:`cli`.
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Invalid Import Name
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```````````````````
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The ``-a`` argument to ``flask`` is the name of the module to import. In
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case that module is incorrectly named you will get an import error upon
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start (or if debug is enabled when you navigate to the application). It
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will tell you what it tried to import and why it failed.
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The most common reason is a typo or because you did not actually create an
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``app`` object.
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.. _debug-mode:
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Debug Mode
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----------
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The :meth:`~flask.Flask.run` method is nice to start a local
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development server, but you would have to restart it manually after each
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change to your code. That is not very nice and Flask can do better. If
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you enable debug support the server will reload itself on code changes,
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and it will also provide you with a helpful debugger if things go wrong.
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The ``flask`` script is nice to start a local development server, but
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you would have to restart it manually after each change to your code.
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That is not very nice and Flask can do better. If you enable debug
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support the server will reload itself on code changes, and it will also
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provide you with a helpful debugger if things go wrong.
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There are two ways to enable debugging. Either set that flag on the
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application object::
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There are different ways to enable the debug mode. The most obvious one
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is the ``--debug`` parameter to the ``flask`` command::
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app.debug = True
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app.run()
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flask --debug -a hello run
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Or pass it as a parameter to run::
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This does the following things:
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app.run(debug=True)
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1. it activates the debugger
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2. it activates the automatic reloader
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3. it enables the debug mode on the Flask application.
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Both methods have the exact same effect.
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There are more parameters that are explained in the :ref:`server` docs.
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.. admonition:: Attention
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@ -236,9 +273,9 @@ below. It tells Flask to behave as though it is handling a request, even
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though we are interacting with it through a Python shell. Have a look at the
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explanation below. :ref:`context-locals`).
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Why would you want to build URLs using the URL reversing function :func:`~flask.url_for`
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instead of hard-coding them into your templates? There are three good reasons
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for this:
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Why would you want to build URLs using the URL reversing function
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:func:`~flask.url_for` instead of hard-coding them into your templates?
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There are three good reasons for this:
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1. Reversing is often more descriptive than hard-coding the URLs. More
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importantly, it allows you to change URLs in one go, without having to
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50
docs/server.rst
Normal file
50
docs/server.rst
Normal file
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@ -0,0 +1,50 @@
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.. _server:
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Development Server
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==================
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.. currentmodule:: flask
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Starting with Flask 1.0 there are multiple built-in ways to run a
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development server. The best one is the ``flask`` command line utility
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but you can also continue using the :meth:`Flask.run` method.
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Command Line
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------------
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The ``flask`` command line script (:ref:`cli`) is strongly recommende for
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development because it provides a superior reload experience due to how it
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loads the application. The basic usage is like this::
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$ flask -a my_application --debug run
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This will enable the debugger, the reloader and then start the server on
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*http://localhost:5000/*.
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The individual features of the server can be controlled by passing more
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arguments to the ``run`` option. For instance the reloader can be
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disabled::
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$ flask -a my_application --debug run --no-reload
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In Code
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-------
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The alternative way to start the application is through the
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:meth:`Flask.run` method. This will immediately launch a local server
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exactly the same way the ``flask`` script does.
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Example::
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if __name__ == '__main__':
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app.run()
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This works well for the common case but it does not work well for
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development which is why from Flask 1.0 onwards the ``flask`` method is
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recommended. The reason for this is that due to how the reload mechanism
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works there are some bizarre side-effects (like executing certain code
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twice, sometimes crashing without message or dieing when a syntax or
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import error happens).
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It is however still a perfectly valid method for invoking a non automatic
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reloading application.
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@ -26,6 +26,16 @@ context.
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Generally it's recommended that you read the :ref:`request-context`
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chapter of the documentation first.
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Command Line Interface
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----------------------
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Starting with Flask 1.0 the recommended way to work with the shell is the
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``flask shell`` command which does a lot of this automatically for you.
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For instance the shell is automatically initialized with a loaded
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application context.
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For more information see :ref:`cli`.
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Creating a Request Context
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--------------------------
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