Working with the Shell

One of the reasons everybody loves Python is the interactive shell. It allows you to play around with code in real time and immediately get results back. Flask provides the flask shell CLI command to start an interactive Python shell with some setup done to make working with the Flask app easier.

.. code-block:: text

$ flask shell

Creating a Request Context

flask shell pushes an app context automatically, so :data:.current_app and :data:.g are already available. However, there is no HTTP request being handled in the shell, so :data:.request and :data:.session are not yet available.

The easiest way to create a proper request context from the shell is by using the :attr:~flask.Flask.test_request_context method which creates us a :class:~flask.ctx.RequestContext:

ctx = app.test_request_context()

Normally you would use the with statement to make this context active, but in the shell it's easier to call :meth:~.RequestContext.push and :meth:~.RequestContext.pop manually:

ctx.push()

From that point onwards you can work with the request object until you call pop:

ctx.pop()

Firing Before/After Request

By just creating a request context, you still don't have run the code that is normally run before a request. This might result in your database being unavailable if you are connecting to the database in a before-request callback or the current user not being stored on the :data:~flask.g object etc.

This however can easily be done yourself. Just call :meth:~flask.Flask.preprocess_request:

ctx = app.test_request_context() ctx.push() app.preprocess_request()

Keep in mind that the :meth:~flask.Flask.preprocess_request function might return a response object, in that case just ignore it.

To shutdown a request, you need to trick a bit before the after request functions (triggered by :meth:~flask.Flask.process_response) operate on a response object:

app.process_response(app.response_class()) <Response 0 bytes [200 OK]> ctx.pop()

The functions registered as :meth:~flask.Flask.teardown_request are automatically called when the context is popped. So this is the perfect place to automatically tear down resources that were needed by the request context (such as database connections).

Further Improving the Shell Experience

If you like the idea of experimenting in a shell, create yourself a module with stuff you want to star import into your interactive session. There you could also define some more helper methods for common things such as initializing the database, dropping tables etc.

Just put them into a module (like shelltools) and import from there:

from shelltools import *