How to Use itertools.product in Python: Syntax and Examples

Use itertools.product in Python to get the Cartesian product of input iterables, which means all possible pairs or tuples combining elements from each iterable. Import it with from itertools import product and call product(iterable1, iterable2, ...) to generate combinations.

Syntax

The itertools.product function syntax is:

• product(*iterables, repeat=1)

Here:

• *iterables means you can pass one or more lists, strings, or other iterable objects.
• repeat is an optional number that repeats the input iterable that many times.

python

from itertools import product

# Basic syntax
product(iterable1, iterable2, ..., repeat=1)

Example

This example shows how to get all pairs from two lists using itertools.product. It prints every combination of one element from the first list with one from the second.

python

from itertools import product

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

for combo in product(colors, sizes):
    print(combo)

Output

('red', 'S')
('red', 'M')
('green', 'S')
('green', 'M')

Common Pitfalls

Common mistakes include:

• Forgetting to import product from itertools.
• Passing non-iterable arguments, which causes errors.
• Not understanding that product returns an iterator, so you need to loop over it or convert it to a list.
• Misusing the repeat argument by passing it without keyword, which can cause confusion.

python

from itertools import product

# Wrong: missing import
# combos = product(['a', 'b'], ['1', '2'])  # NameError

# Wrong: passing non-iterable
# combos = product(5, ['x', 'y'])  # TypeError

# Right: convert to list to see all combos
combos = list(product(['a', 'b'], ['1', '2']))
print(combos)

# Using repeat keyword
combos_repeat = list(product(['a', 'b'], repeat=2))
print(combos_repeat)

Output

[('a', '1'), ('a', '2'), ('b', '1'), ('b', '2')]
[('a', 'a'), ('a', 'b'), ('b', 'a'), ('b', 'b')]

Quick Reference

Summary tips for itertools.product:

• Use it to get all combinations of multiple iterables.
• It returns an iterator, so loop or convert to list to access results.
• The repeat argument repeats the input iterable multiple times.
• Works with any iterable: lists, strings, tuples, etc.

Key Takeaways

Import product from itertools to use it.

product generates all possible tuples combining elements from input iterables.

Remember product returns an iterator; convert to list or loop to access items.

Use the repeat argument to repeat the same iterable multiple times.

Pass only iterable objects to avoid errors.