The Best Way to Loop a list “Infinitely” in Python

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When working with sequences in Python, you might encounter situations where you need to loop through a list repeatedly without manually resetting the index. This is where itertools.cycle() comes to the rescue!

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What is itertools.cycle()?

The cycle() function from the itertools module creates an iterator that continuously loops over the elements of an iterable. Once it reaches the last element, it starts again from the beginning, making it ideal for cases where infinite iteration is required.

How to Use itertools.cycle()

Using cycle() is simple. Here’s a basic example where we cycle through a list of colours:

from itertools import cycle

colors = ["red", "green", "blue"]
color_cycle = cycle(colors)

# Print 10 elements from the cycle
for _ in range(10):
    print(next(color_cycle))

Output:

red
green
blue
red
green
blue
red
green
blue
red

Practical Applications

1. Round-robin scheduling — Distributing tasks cyclically among a group.