Loops are essential in any programming language. Python’s for loop is simple yet incredibly powerful, allowing you to iterate over lists, strings, dictionaries, sets, and more with elegant syntax.

This guide will cover:

• What for loops are and how they work

• Looping over different data types

• Using range()

• Nested loops

• Controlling loops with break and continue

• Tips and common pitfalls

• A complete example

✅ What Is a for Loop?

A for loop in Python is used to iterate over a sequence (like a list, tuple, dictionary, set, or string).

Syntax

for variable in sequence:
    # code block

• variable: Temporary placeholder for each item in the sequence.

• sequence: A collection of items to loop through.

Example 1: Looping Over a List

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

for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

Example 2: Looping Over a String

for char in "Python":
    print(char)

Example 3: Using range()

range() generates a sequence of numbers, which is often used for looping a specific number of times.

for i in range(5):
    print(i)

Output:

0
1
2
3
4

range(5) produces numbers from 0 to 4 (not inclusive of 5).

range(start, stop, step) Example

for i in range(1, 10, 2):
    print(i)

Output:

1
3
5
7
9

Example 4: Looping Over a Dictionary

student = {"name": "Alice", "age": 20, "grade": "A"}

for key, value in student.items():
    print(f"{key}: {value}")

Example 5: Looping Over a Set or Tuple

colors = {"red", "green", "blue"}

for color in colors:
    print(color)

Note: Sets are unordered, so output order may vary.

Nested for Loops

A loop inside another loop.

for i in range(1, 4):
    for j in range(1, 4):
        print(f"{i} * {j} = {i*j}")

Exiting Loops Early – break

for i in range(5):
    if i == 3:
        break
    print(i)

Output:

0
1
2

Skipping Iterations – continue

for i in range(5):
    if i == 2:
        continue
    print(i)

Output:

0
1
3
4

➕ The else Clause

Python’s for loops can have an else block, which executes only if the loop completes without a break.

for i in range(3):
    print(i)
else:
    print("Loop completed successfully!")

Common Pitfalls

Tips and Best Practices

• Use enumerate() to get index and value:

  for index, value in enumerate(["a", "b", "c"]):
      print(index, value)
  

• Use zip() to loop over multiple lists together:

  names = ["Alice", "Bob"]
  scores = [85, 90]
  for name, score in zip(names, scores):
      print(f"{name} scored {score}")
  

• Use reversed() and sorted() with any iterable:

  for num in reversed(range(5)):
      print(num)
  

Complete Example: Multiplication Table

for i in range(1, 6):
    for j in range(1, 6):
        print(f"{i * j:2}", end=" ")
    print()

Output:

 1  2  3  4  5
 2  4  6  8 10
 3  6  9 12 15
 4  8 12 16 20
 5 10 15 20 25

What’s Next?

After learning for loops, you can explore:

• Comprehensions: List/set/dictionary comprehensions using for

• Generators and iterators

• Looping through files or API results

• Combining with if conditions inside loops

Practice Challenge

Task: Write a program that finds the factorial of a given number using a for loop.

num = int(input("Enter a number: "))
factorial = 1

for i in range(1, num + 1):
    factorial *= i

print("Factorial is", factorial)