Python is Iterable (iterator), generator (generator), yield
Iterator:
We usually use the list, it is an iterator. Possible to read each element in the list by a for loop.
All can be traversed in both iterators through .. for . Such as lists, strings, files
Builder:
When the iterator declaration or a list of strings, when too much of the contents of their memory, will take up more memory. This time the role of generators began to unravel.