On 12/12/2009 8:24 AM, Peter Otten wrote:
But it is inefficient, because it is matching the regex twice for each
item, and it is a bit ugly.
I could use:
n = []
for x in keys:
m = r.match(x)
if m:
n.append(m.group(1))
It is more efficient, but much uglier.
It's efficient and easy to understand; maybe you have to readjust your
taste.
I agree, it's easy to understand, but it's also ugly because of the
level of indentation (which is too deep for such a simple problem).
Does anyone have a better solution?
(sorry to ramble around)
A few months ago, I suggested an improvement in the python-ideas list to
add a post-filter to list-comprehension, somewhere in this line:
a = [f(x) as F for x in l if c(F)]
where the evaluation of f(x) will be the value of F so F can be used in
the if-expression as a post-filter (complementing list-comps' pre-filter).
Many doubted its usefulness since they say it's easy to wrap in another
list-comp:
a = [y for y in (f(x) for x in l) if c(y)]
or with a map and filter
a = filter(None, map(f, l))
Up till now, I don't really like the alternatives.
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