map/filter/reduce/lambda opinions and background unscientificmini-survey
tjreedy at udel.edu
Thu Jul 7 22:36:29 CEST 2005
"Pawe³ Sakowski" <pawel at sakowski.pl> wrote in message
news:dajghf$dit$1 at inews.gazeta.pl...
Tom Anderson wrote:
> def flatten(ll):
> return reduce(lambda a, l: a.extend(l), ll, )
> How would one do that as a list comp, by the way? I'm really not very
> with them yet.
Not really a list-comprehension based solution, but I think what you want
[1, 2, 3, 4, 5, 6]
Unless sum knows to typecheck input items and special-case lists and use
list.extend rather than list+list, this turns an O(n) operation into an
O(n**2) operation. Sum is meant for numbers.
Terry J. Reedy
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