RFC: Assignment as expression (pre-PEP)

[Georg Brandl]

Alex Martelli schrieb:
> Adam Atlas <adam at atlas.st> wrote:
> 
>> Hasn't this been discussed many many times before? I think Guido has
>> been favourable to the idea of allowing :=, but that was a long time
>> ago, and I don't think anything ever came of it.
>> 
>> Personally, if anything, I'd like to see more use of the 'as' keyword
>> as in Python 2.5's new 'with' statement. Assignment is basically what
>> it adds to the statement, so if anything we should reuse it in other
>> statements for consistency.
>> 
>> if my_re1.match(exp) as temp:
>>   # do something with temp
>> elif my_re2.match(exp) as temp:
>>   # do something with temp
>> elif my_re3.match(exp) as temp:
>>   # do something with temp
>> elif my_re4.match(exp) as temp:
>>   # do something with temp
>> 
>> As others have mentioned, your particular instance is probably
>> evidence that you need to restructure your code a little bit, but I do
>> agree that "x = y; if x: ..." is a common enough idiom that it
>> warrants a shortcut. And reusing "as", I think, is nice and readable,
>> and it's an advantage that it doesn't require adding any new keywords
>> or symbols.
> 
> Actually, I agree with you.  Unfortunately, I doubt python-dev will, but
> the chance is good enough that it's probably worth proposing there
> (ideally together with a patch to implement it, just to avoid any
> [otherwise likely] whines about this being difficult to implement:-).

The patch is already done -- I have it lying around here :)

Georg

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