Message113421
Sometimes it's useful to get the number of elements yield by an iterator. For example (if ilen is the name of the function):
def pi(n):
return ilen(for e in xrange(n) if isprime(e))
def count_pred(pred, iterator):
return ilen(itertools.ifilter(pred, iterator))
Two notable solutions are discussed here http://stackoverflow.com/questions/3393431/how-to-counting-not-0-elements-in-an-iterable
1) sum(1 for e in iterator)
2) len(list(iterator))
First solution is slow, the second solution uses O(N) extra memory.
I propose the addition of a new function ilen() which is functionally equivalent to:
def ilen(iterator):
return sum(1 for e in iterator)
This function should be different from len() because it's time complexity is O(N) (most people assume that len() takes O(1)) and it consumes the iterator. |
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Date |
User |
Action |
Args |
2010-08-09 16:16:01 | Alexandru.Moșoi | set | recipients:
+ Alexandru.Moșoi |
2010-08-09 16:16:01 | Alexandru.Moșoi | set | messageid: <1281370561.47.0.585215134028.issue9547@psf.upfronthosting.co.za> |
2010-08-09 16:15:59 | Alexandru.Moșoi | link | issue9547 messages |
2010-08-09 16:15:59 | Alexandru.Moșoi | create | |
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