pythoniterator

Getting number of elements in an iterator in Python

Is there an efficient way to know how many elements are in an iterator in Python, in general, without iterating through each and counting?

Solution

  • No. It's not possible.

    Example:

    import random

def gen(n):
    for i in xrange(n):
        if random.randint(0, 1) == 0:
            yield i

iterator = gen(10)

    Length of iterator is unknown until you iterate through it.