Getting number of elements in an iterator in Python

No, any method will require you to resolve every result. You can do

iter_length = len(list(iterable))

but running that on an infinite iterator will of course never return. It also will consume the iterator and it will need to be reset if you want to use the contents.

Telling us what real problem you're trying to solve might help us find you a better way to accomplish your actual goal.

Edit: Using list() will read the whole iterable into memory at once, which may be undesirable. Another way is to do

sum(1 for _ in iterable)

as another person posted. That will avoid keeping it in memory.