Improve clarity of try-return-finally-return (GH-15677)

Clarify execution in try-return-finally-return case.
This commit is contained in:
toonarmycaptain 2019-09-11 10:37:13 -05:00 committed by Stéphane Wirtel
parent 4a12a178f4
commit 0cc27417f2
2 changed files with 23 additions and 9 deletions

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@ -388,15 +388,28 @@ example::
File "<stdin>", line 2, in <module>
KeyboardInterrupt
A *finally clause* is always executed before leaving the :keyword:`try`
statement, whether an exception has occurred or not. When an exception has
occurred in the :keyword:`!try` clause and has not been handled by an
:keyword:`except` clause (or it has occurred in an :keyword:`!except` or
:keyword:`!else` clause), it is re-raised after the :keyword:`finally` clause has
been executed. The :keyword:`!finally` clause is also executed "on the way out"
when any other clause of the :keyword:`!try` statement is left via a
:keyword:`break`, :keyword:`continue` or :keyword:`return` statement. A more
complicated example::
If a :keyword:`finally` clause is present, the :keyword:`finally` clause will execute as the last task before the :keyword:`try` statement completes. The :keyword:`finally` clause runs whether or not the :keyword:`try` statement produces an exception. The following points discuss more complex cases when an exception occurs:
* If an exception occurs during execution of the :keyword:`!try` clause, the exception may be handled by an :keyword:`except` clause. In all cases, the exception is re-raised after the :keyword:`!finally` clause has been executed.
* An exception could occur during execution of an :keyword:`!except` or :keyword:`!else` clause. Again, the exception is re-raised after the :keyword:`!finally` clause has been executed.
* If the :keyword:`!try` statement reaches a :keyword:`break`, :keyword:`continue` or :keyword:`return` statement, the :keyword:`finally` clause will execute just prior to the :keyword:`break`, :keyword:`continue` or :keyword:`return` statement's execution.
* If a :keyword:`finally` clause includes a :keyword:`return` statement, the :keyword:`finally` clause's :keyword:`return` statement will execute before, and instead of, the :keyword:`return` statement in a :keyword:`try` clause.
For example::
>>> def bool_return(): -> bool:
... try:
... return True
... finally:
... return False
...
>>> bool_return()
False
A more complicated example::
>>> def divide(x, y):
... try:

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@ -58,6 +58,7 @@ Jon Anglin
Michele Angrisano
Ankur Ankan
Heidi Annexstad
David Antonini
Ramchandra Apte
Éric Araujo
Alexandru Ardelean