Loops are how we automate repetition in code. But beyond just for and while, Python gives us powerful built-in tools like enumerate(), zip(), and the entire itertools module for smarter, cleaner, and more powerful iterations.

In this post, you’ll learn:

• All about for and while loops (with deeper examples)
• How to iterate with enumerate() and zip()
• What range() actually does and why it’s so powerful
• Why itertools is a hidden gem for developers
• Real-world scenarios like combinations, counters, and grouped data

🔁 Revisiting the Basics: for and while

for Loop Recap:

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(f"I like {fruit}")

while Loop Recap:

count = 0
while count < 3:
    print("Count is:", count)
    count += 1

🔍 The range() Function (Super Useful)

Syntax:

range(start, stop, step)

• start: where to begin (default = 0)
• stop: where to end (not included)
• step: how much to increase by (default = 1)

Examples:

for i in range(5):        # 0 to 4
    print(i)

for i in range(1, 6):     # 1 to 5
    print(i)

for i in range(10, 0, -2):  # Countdown by 2s
    print(i)

📍 enumerate() Loop with Index

names = ["Ali", "Fatima", "Sara"]

for index, name in enumerate(names):
    print(f"{index}: {name}")

Output:
0: Ali
1: Fatima
2: Sara

🔗 zip() Loop Through Multiple Lists

students = ["Ali", "Fatima", "Sara"]
marks = [88, 92, 77]

for name, mark in zip(students, marks):
    print(f"{name} scored {mark}")

Output:
Ali scored 88
Fatima scored 92
Sara scored 77

✅ Tip:

If lists are of unequal length, zip() stops at the shortest one.

📚 Introducing itertools – Python’s Loop Power Tools

itertools is a standard Python module that provides functions to:

• Create infinite or advanced iterators
• Work with combinations, permutations, grouping
• Chain or filter multiple iterable sources

✅ Importing It:

import itertools

🔄 itertools.count() – Infinite Counter

from itertools import count

for num in count(5):
    if num > 10:
        break
    print(num)

Output:
5
6
7
8
9
10

♾️ itertools.cycle() – Loop Forever Through a List

from itertools import cycle

colors = ["red", "green", "blue"]

for color in cycle(colors):
    print(color)
    # Use break or limit it!

Use with caution it’s infinite by default.

📦 itertools.chain() – Combine Multiple Lists

from itertools import chain

a = [1, 2]
b = [3, 4]

for item in chain(a, b):
    print(item)

Output: 1 2 3 4

🔢 itertools.combinations() – Pick Unique Pairs

from itertools import combinations

players = ["Ali", "Fatima", "Sara"]

for combo in combinations(players, 2):
    print(combo)

Output:
(‘Ali’, ‘Fatima’)
(‘Ali’, ‘Sara’)
(‘Fatima’, ‘Sara’)

🔁 itertools.permutations() – All Possible Orders

from itertools import permutations

for p in permutations([1, 2, 3]):
    print(p)

Output:
All 6 possible orderings of [1, 2, 3]

🧮 itertools.groupby() – Group Consecutive Data

from itertools import groupby

data = [1, 1, 2, 2, 2, 3, 1, 1]

for key, group in groupby(data):
    print(key, list(group))

Output:
1 [1, 1]

2 [2, 2, 2]

3 [3]

1 [1, 1]

📌 Want to go beyond loops and try a cleaner, functional style?
Read our post on Functional Programming in Python to learn how to use map(), filter(), lambda, and generators.

⚠️ Common Looping Mistakes