For review: PEP 343: Anonymous Block Redux and Generator Enhancements

[Nicolas Fleury]

Andrew Dalke wrote:
>>def foo():
>>     with locking(someMutex)
>>         with opening(readFilename) as input
>>             with opening(writeFilename) as output
>>                 ...
> 
> 
> Nothing in Python ends at the end of the current block.
> They only end with the scope exits.  The order of deletion
> is not defined, and you would change that as well.

There's no change in order of deletion, it's just about defining the 
order of calls to __exit__, and they are exactly the same.  As far as I 
know, PEP343 has nothing to do with order of deletion, which is still 
implementation-dependant.  It's not a constructor/destructor thing like 
in C++ RAII, but __enter__/__exit__.

But yes, it creates a precedent by creating a statement affecting the 
end of the current indentation block.  But that's what this PEP is all 
about...

> Your approach wouldn't allow the following

No, I said making the ':' *optional*.  I totally agree supporting ':' is 
useful.

> If the number of blocks is a problem it wouldn't be that
> hard to do
> 
> with multi( locking(someMutex),
>             opening(readFilename),
>             opening(writeFilename) ) as _, input, output:
>   ...

True.  But does it look as good?  Particularly the _ part?

Regards,
Nicolas