For review: PEP 308 - If-then-else expression

Greg Ewing (using news.cis.dfn.de) me at privacy.net
Tue Feb 11 03:34:23 CET 2003


Andrew Dalke wrote:

> Part of the reason it
> hasn't been a problem is that few people do
>    [x, y for x in list1 for y in [for z in spam] if x*y > 9.801]


Assuming you meant

    [x, y for x in list1 for y in [z for z in spam] if x*y > 9.801]

the nested LC in there is redundant; this is equivalent to

    [x, y for x in list1 for y in spam if x*y > 9.801]

I'm not sure, but it may even be a theorem that any nested
LC can be re-written as a non-nested LC by pulling all the
loops out to the top level and combining the target expressions
appropriately.

-- 
Greg Ewing, Computer Science Dept,
University of Canterbury,	
Christchurch, New Zealand
http://www.cosc.canterbury.ac.nz/~greg





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