mirror of https://github.com/mitsuhiko/flask.git
Armin Ronacher
15 years ago
8 changed files with 215 additions and 81 deletions
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User's Guide |
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------------ |
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This part of the documentation is written text and should give you an idea |
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how to work with Flask. It's a series of step-by-step instructions for |
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web development. |
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.. toctree:: |
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:maxdepth: 2 |
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foreword |
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installation |
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quickstart |
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tutorial/index |
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testing |
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errorhandling |
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shell |
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patterns/index |
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deploying/index |
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becomingbig |
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API Reference |
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------------- |
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If you are looking for information on a specific function, class or |
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method, this part of the documentation is for you. |
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.. toctree:: |
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:maxdepth: 2 |
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api |
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Additional Notes |
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---------------- |
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Design notes, legal information and changelog are here for the interested. |
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.. toctree:: |
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:maxdepth: 2 |
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design |
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license |
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changelog |
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Working with the Shell |
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====================== |
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.. versionadded:: 0.5 |
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One of the reasons everybody loves Python is the interactive shell. It |
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basically allows you to execute Python commands in real time and |
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immediately get results back. Flask itself does not come with an |
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interactive shell, because it does not require any specific setup upfront, |
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just import your application and start playing around. |
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There are however some handy helpers to make playing around in the shell a |
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more pleasant experience. The main issue with interactive console |
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sessions is that you're not triggering a request like a browser does which |
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means that :data:`~flask.g`, :data:`~flask.request` and others are not |
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available. But the code you want to test might depend on them, so what |
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can you do? |
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This is where some helper functions come in handy. Keep in mind however |
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that these functions are not only there for interactive shell usage, but |
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also for unittesting and other situations that require a faked request |
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context. |
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Diving into Context Locals |
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-------------------------- |
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Say you have a utility function that returns the URL the user should be |
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redirected to. Imagine it would always redirect to the URL's ``next`` |
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parameter or the HTTP referrer or the index page:: |
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from flask import request, url_for |
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def redirect_url(): |
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return request.args.get('next') or \ |
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request.referrer or \ |
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url_for('index') |
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As you can see, it accesses the request object. If you try to run this |
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from a plain Python shell, this is the exception you will see: |
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>>> redirect_url() |
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Traceback (most recent call last): |
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File "<stdin>", line 1, in <module> |
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AttributeError: 'NoneType' object has no attribute 'request' |
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That makes a lot of sense because we currently do not have a request we |
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could access. So we have to make a request and bind it to the current |
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context. The :attr:`~flask.Flask.test_request_context` method can create |
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us a request context: |
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>>> ctx = app.test_request_context('/?next=http://example.com/') |
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This context can be used in two ways. Either with the `with` statement |
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(which unfortunately is not very handy for shell sessions). The |
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alternative way is to call the `push` and `pop` methods: |
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>>> ctx.push() |
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From that point onwards you can work with the request object: |
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>>> redirect_url() |
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u'http://example.com/' |
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Until you call `pop`: |
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>>> ctx.pop() |
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>>> redirect_url() |
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Traceback (most recent call last): |
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File "<stdin>", line 1, in <module> |
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AttributeError: 'NoneType' object has no attribute 'request' |
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Firing Before/After Request |
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--------------------------- |
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By just creating a request context, you still don't have run the code that |
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is normally run before a request. This probably results in your database |
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being unavailable, the current user not being stored on the |
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:data:`~flask.g` object etc. |
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This however can easily be done yourself. Just call |
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:meth:`~flask.Flask.preprocess_request`: |
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>>> ctx = app.test_request_context() |
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>>> ctx.push() |
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>>> app.preprocess_request() |
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Keep in mind that the :meth:`~flask.Flask.preprocess_request` function |
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might return a response object, in that case just ignore it. |
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To shutdown a request, you need to trick a bit before the after request |
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functions (triggered by :meth:`~flask.Flask.process_response`) operate on |
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a response object: |
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>>> app.process_response(app.response_class()) |
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<Response 0 bytes [200 OK]> |
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>>> ctx.pop() |
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Further Improving the Shell Experience |
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-------------------------------------- |
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If you like the idea of experimenting in a shell, create yourself a module |
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with stuff you want to star import into your interactive session. There |
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you could also define some more helper methods for common things such as |
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initializing the database, dropping tables etc. |
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Just put them into a module (like `shelltools` and import from there): |
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>>> from shelltools import * |
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