On 03/20/2011 09:44 PM, bearophile wrote:
> # Logically, the following should produce a copy:
> [x in coll] # dont work
Your logic is broken.
I don't think so ;-) This is something I discussed on Python's design mailing
list ("ideas"). The only reason why this is not possible to implement in python
is that 'in' is also the membership operator. So that [x in coll] evaluates to
[true] or [false]. Just replace 'in' by another keyword in the expression of
list comprehensions, and, I guess, you won't find it broken:
# filter only:
negs = [x across coll if x<1]
instead of
# current syntax forces mapping with identity function
# in addition to filter:
negs = [x for x in coll if x<1]
What's really weird is that mapping without filter is indeed possible; one is
not forced to write:
squares = [x*x for x in coll if true]
lol!
Denis
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