itertools module provides a number of functions that we can use to produce finite sequences of values. We'll look at ten functions in this module, plus some related built-in functions:
enumerate(): This function is actually part of the
__builtins__package, but it works with an iterator and is very similar to other functions in the
accumulate(): This function returns a sequence of reductions of the input iterable. It's a higher-order function and can do a variety of clever calculations.
chain(): This function combines multiple iterables serially.
groupby(): This function uses a function to decompose a single iterable into a sequence of iterables over subsets of the input data.
zip_longest(): This function ...