python for loop, iterator, iterable, generator

For Loop
 When Python executes the for loop, it first invokes the __iter__() method of the container to get the iterator of the container. It then repeatedly calls the next() method (__next__() method in Python 3.x) of the iterator until the iterator raises a StopIteration exception. Once the exception is raised, the for loop ends.

Generators can be thought of as resumable functions