Python – Itertools.chain.from_iterable()

Python’s Itertool is a module that provides various functions that work on iterators to produce complex iterators. This module works as a fast, memory-efficient tool that is used either by themselves or in combination to form iterator algebra.

Note: For more information, refer to Python Itertools

The functions under itertools can be classified into 3 categories

1. Functions producing Infinite Iterators
2. Functions producing Iterators terminating on the shortest input sequence
3. Functions producing Combinatoric generators

Chain.from_iterable() method

The function chain.from_iterable() comes under the category of terminating iterators. This function takes a single iterable as an argument and all the elements of the input iterable should also be iterable and it returns a flattened iterable containing all the elements of the input iterable.

Syntax :
chain.from_iterable(iterable)

Example #1:

# Importing chain class from itertools
from itertools import chain


# Single iterable containing iterable
# elements(strings) is passed as input
from_iterable = chain.from_iterable(['geeks',
                                     'for',
                                     'geeks'])

# printing the flattened iterable
print(list(from_iterable))

Output :

[‘g’, ‘e’, ‘e’, ‘k’, ‘s’, ‘f’, ‘o’, ‘r’, ‘g’, ‘e’, ‘e’, ‘k’, ‘s’]

Example #2:

# Importing chain class from itertools
from itertools import chain


# Single iterable containing iterable
# elements(strings and list) is passed
# as input
from_iterable = chain.from_iterable(['geeks',
                                     'for',
                                     'geeks',
                                     ['w', 'i', 'n', 's']])

# printing the flattened iterable
print(list(from_iterable))

Output :

[‘g’, ‘e’, ‘e’, ‘k’, ‘s’, ‘f’, ‘o’, ‘r’, ‘g’, ‘e’, ‘e’, ‘k’, ‘s’, ‘w’, ‘i’, ‘n’, ‘s’]