itertools.chain() vs itertools.chain.from_iterable()
itertools.chain() and itertools.chain.from_iterable() are both Python Itertools Module APIs, and choosing between them is a common point of confusion. This page compares their syntax, parameters, return values, and typical use cases so you can pick the right one. itertools.chain(): Creates an iterator that returns elements from the first iterable until exhausted, then proceeds to the next. Its syntax is itertools.chain(*iterables), and it returns iterator itertools.chain.from_iterable(): Alternative chain that takes a single iterable of iterables. Its syntax is itertools.chain.from_iterable(iterable), and it returns iterator Example of itertools.chain(): from itertools import chain
list(chain([1,2], [3,4])) # [1,2,3,4]. Example of itertools.chain.from_iterable(): list(chain.from_iterable([[1,2],[3,4]])) # [1,2,3,4]. Read the full references for itertools.chain() and itertools.chain.from_iterable() to see parameters, edge cases, and example code side by side. Other Itertools Module APIs worth comparing: itertools.product(), itertools.permutations(), itertools.combinations(), itertools.combinations_with_replacement(), itertools.cycle(), itertools.repeat(). Both belong to the Itertools Module category in the Python Reference documentation.