Before we understand generator we must know Iterator.
Iterator:
Iterator is any object which understands the concept of a for-loop.
Basically this means that it has a next method, when it is called it returns the next item in the sequence.
Everything you can use in "for" is an iterable: lists, strings, files...etc
>>> [x*x for x in range(3)]
[0, 1, 4]
>>> mylist = [x*x for...