[Python-ideas] iterator length
brtzsnr at gmail.com
Mon Aug 9 22:17:23 CEST 2010
2010/8/9 Paul Moore <p.f.moore at gmail.com>:
> If you could show some real code that uses your ilen function, that
> would help clarify. But it still won't explain why the function should
> be built in rather than just defined by your code where it's needed -
> you'll have to have some very common and compelling use cases to argue
My requirements was to count the non-zero elements from a list like this:
sum(1 for e in iterator if not e)
What I'm really looking for is the number of elements in a list comprehension:
len(list(for e in iterator if not e))
but this is not generally useful nor optimal in terms of memory requirements.
My idea was to implement the above with the aid of itertools.ifilter:
if pred is None, this would translate in my usecase.
Since I first post this I learned that ilen (or something similar) was
rejected before due to similar concerns: it consumes the iterator,
it's not a real optimization.
How about: count(pred, iterable) which returns the same value as
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