[Python-ideas] with-except-finally blocks

[Andrew Barnert]

On Thursday, April 16, 2015 12:33 AM, James Edwards <jheiv at jheiv.com> wrote:

> > On Thu, Apr 16, 2015 at 3:22 AM, Andrew Barnert
> <abarnert at yahoo.com.dmarc.invalid> wrote:
>>  Anyway, I like the idea, but does the grammar work? A with that has an 
> optional except and finally at the same level seems potentially ambiguous. For 
> example:
>> 
>>      with spam:
>>          pass
>>      with eggs:
>>          pass
>>      finally:
>>          pass
> 
> Is this any more (or less) ambiguous than:
> 
>     if cond1:
>         pass
>     if cond2:
>         pass
>     else:
>         pass
> 
> And we have no issue with that (at least not syntactically).

Duh.

Just to make sure, I hacked up a quick patch. (Diff attached.) This gets you enough to test the syntax:

    $ ./python.exe
    >>> import ast
    >>> print(ast.dump(ast.parse('with:\n pass\nwith:\n pass\nfinally:\n pass\n')))
    Module(body=[With(items=[withitem(context_expr=Name(id='spam', ctx=Load()), optional_vars=None)], body=[Pass()], handlers=[], orelse=[], finalbody=[]), With(items=[withitem(context_expr=Name(id='eggs', ctx=Load()), optional_vars=None)], body=[Pass()], handlers=[], orelse=[], finalbody=[]), With(items=[], body=[Pass()], handlers=[], orelse=[], finalbody=[Pass()])])

That's one With statement with no except/else/finally, and one With statement with a finally, just as you'd expect.

(Of course the compiler just ignores the except/else/finally bits.)
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