Iterator python

Iterators are widely used in python. It seems modern C++ is also using iterators to improve efficiency.

A good introduction about iterator can be found here.

Python Iterators

A good application of using iterator can be found from the post below.

https://leetcode.com/problems/number-of-matching-subsequences/discuss/117634/Efficient-and-simple-go-through-words-in-parallel-with-explanation