Flask official tutorial: what is 'e' in close_db(e=None)?

Question

In Flask’s tutorial [here], the definition for close_db included a default value for ‘e=None’. But, this value isn’t used in the function nor I can find reference anywhere.

def close_db(e=None):
    db = g.pop('db', None)

    if db is not None:
        db.close()

Is there any specific reasons ‘e=None’ is explicitly stated?

Asked By: techtana

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Source

Answer 1

You’ll notice in the tutorial that in the init_app function, close_db is passed as an argument to app.teardown_appcontext().

From the docstring for teardown_appcontext:

When a teardown function was called because of an unhandled exception
it will be passed an error object. If an errorhandler is
registered, it will handle the exception and the teardown will not
receive it.

So e refers to the error object, which is None by default. You can learn more about registering error handlers at this link.

Answered By: JoshG

Flask official tutorial: what is 'e' in close_db(e=None)?

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