[Python-ideas] Is this PEP-able? for X in ListY while conditionZ:

[jimjhb at aol.com]

I saw your thread.  Thank you for summarizing the result!  It looks like the best alternative is itertools.takewhile, but I don't like it....  :(

-Jim


-----Original Message-----
From: Wolfgang Maier <wolfgang.maier at biologie.uni-freiburg.de>
To: python-ideas <python-ideas at python.org>
Sent: Tue, Jun 25, 2013 4:51 pm
Subject: Re: [Python-ideas] Is this PEP-able? for X in ListY while	conditionZ:


Hi,
I suggested the very same 'while in a comprehension/generator expression'
back in January:
http://mail.python.org/pipermail/python-ideas/2013-January/018969.html

There were many very useful responses suggesting alternative syntax (that
I'm using now).
The proposal itself was dismissed with the logic that comprehensions can
currently be translated directly into explicit for loops, e.g.:

[x for x in items if x!=0]

equals:

result=[]
for x in items:
    if x!=0:
        result.append(x)

This equivalence is considered *very* important and the while statement
would break it:

[x for x in items while x>0]

does *not* translate into:

for x in item:
    while x>0:
        result.append(x)

So, as long as you can't come up with syntax that translates properly,
there's no chance of getting it accepted.

Best,
Wolfgang


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