Generators¶

Sometimes we want to call something before and after original function call.

That purpouse can be reached by using yield keyword.

A database dependency with yield¶

For example, you could use this to create a database session and close it after finishing.

Only the code prior yield statement is executed before sending a response

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def dependency():
    db = DBSession()
    yield db
    db.close()

The yielded value is what is injected into original function

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def dependency():
    db = DBSession()
    yield db
    db.close()

The code following the yield statement is executed after the original function has been called

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def dependency():
    db = DBSession()
    yield db
    db.close()

All errors occurs at original function or another dependencies will be raised this place

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def dependency():
    db = DBSession()
    yield db
    db.close()

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def dependency():
    db = DBSession()
    try:
        yield db
    finally:
        db.close()