return from finally clause

[Tim Peters]

[Jürgen Hermann]
> Consider this script:
>
> def spam(ret):
>     try:
>         print 1
>         try:
>             print 2
>             raise RuntimeError
>         finally:
>             print 3
>             if ret: return
>     finally:
>         print 4
>     print 5
>
> spam(1)
> spam(0)
>
> and its output
>
> 1
> 2
> 3
> 4
> 1
> 2
> 3
> 4
> Traceback (most recent call last):
>   File "exp.py", line 15, in ?
>     spam(0)
>   File "exp.py", line 6, in spam
>     raise RuntimeError
> RuntimeError
>
> That means that if you (accidently?) return within a finally clause, you
> effectively eat the exception.

It also means that if you deliberately return within a finally clause, you
deliberately eat the exception.  This is like saying that if you add one to
a number accidentally, the number's value increases anyway <wink>.

> This should be documented, or fixed.

Aren't the docs already clear?:

    http://www.python.org/doc/current/ref/try.html
    ...
    If the finally clause raises another exception or executes a
    return or break statement, the saved exception is lost.
    ...

When use a finally block, you're explictly saying "NO MATTER WHAT--
exception or no exception --do the stuff in this block".  If that stuff
includes a return, Python returns.  You'll find the same behavior in Java
(among others).