[Python-Dev] "as" mania

[Georg Brandl]

Alex Martelli wrote:

> I think the best use cases for 'assignment inside an if or while'  
> condition, as far as they go, require `capturing' a SUB-expression of  
> the condition, rather than the whole condition.  E.g., in C,
> 
> while ( (x=next_x()) < threshold ) ...
> 
> being able to capture (by `as') only the whole (true or false)  
> condition meets a minority of the use cases, so I'm unenthusiastic  
> about it.

There are use cases (because every value can be tested for true-ness), such
as the likes of

while file.readline() as line:
    BLOCK

(which is not needed for builtin file objects, I know)

or something like

m = re.match(...)
if m.group(1) as filename:
    do something with filename


Georg