product - Cartesian Product

The product() function computes the Cartesian product of input iterables, generating all ordered tuples by selecting one element from each iterable. It replaces nested for-loops with a single flat iterator, producing more concise code and avoiding deep indentation when iterating over multiple dimensions.

Basic Cartesian Product

Pass two or more iterables to product() and it yields every possible ordered tuple containing one element from each. This is equivalent to nested for-loops but expressed as a single flat iterator.

from itertools import product

colors = ['red', 'green']
sizes = ['S', 'M', 'L']

combinations = list(product(colors, sizes))
print(combinations)

[('red', 'S'), ('red', 'M'), ('red', 'L'), ('green', 'S'), ('green', 'M'), ('green', 'L')]

Multiple Iterables and Repeat

The repeat parameter specifies how many times the input iterable is repeated in the product. product(A, repeat=3) is equivalent to product(A, A, A).

from itertools import product

# Pairs from a single iterable
pairs = list(product([1, 2, 3], repeat=2))
print(pairs)

# Self-product with 3 iterations
triples = list(product('AB', repeat=3))
print(triples)

[(1, 1), (1, 2), (1, 3), (2, 1), (2, 2), (2, 3), (3, 1), (3, 2), (3, 3)]
[('A', 'A', 'A'), ('A', 'A', 'B'), ('A', 'B', 'A'), ('A', 'B', 'B'), ('B', 'A', 'A'), ('B', 'A', 'B'), ('B', 'B', 'A'), ('B', 'B', 'B')]