For Loops

Introduction

A for loop iterates over a sequence — a list, string, range, or any iterable — and runs the same block of code for each item.

Basic Syntax

for variable in sequence:
    # code to run for each item

Iterating Over a List

employees = ["Alice", "Bob", "Charlie"]

for employee in employees:
    print(employee)

Output

Alice
Bob
Charlie

Using range()

range() generates a sequence of numbers. It is commonly used when you need to repeat something a set number of times.

# range(stop) — 0 up to (but not including) stop
for i in range(5):
    print(i)
# 0, 1, 2, 3, 4

# range(start, stop)
for i in range(2, 6):
    print(i)
# 2, 3, 4, 5

# range(start, stop, step)
for i in range(0, 10, 2):
    print(i)
# 0, 2, 4, 6, 8

Iterating Over a String

Strings are sequences of characters — you can loop over them directly.

for char in "Python":
    print(char)

Output

P
y
t
h
o
n

break and continue

break exits the loop immediately. continue skips the rest of the current iteration and moves to the next.

salaries = [30000, 55000, 80000, 120000, 45000]

for salary in salaries:
    if salary > 100000:
        print("Found a high earner, stopping")
        break
    print(salary)

for i in range(10):
    if i % 2 == 0:
        continue   # skip even numbers
    print(i)
# 1, 3, 5, 7, 9

enumerate()

When you need both the index and the value, use enumerate().

employees = ["Alice", "Bob", "Charlie"]

for index, name in enumerate(employees):
    print(f"{index + 1}. {name}")

Output

1. Alice
2. Bob
3. Charlie

List Comprehensions

A compact way to create a list using a for loop in a single line.

# Standard loop
squares = []
for n in range(1, 6):
    squares.append(n ** 2)

# List comprehension — same result
squares = [n ** 2 for n in range(1, 6)]

print(squares)  # [1, 4, 9, 16, 25]

Practice Exercises

• Loop over a list of five product names and print each one.
• Use range() to print the numbers 1 to 10.
• Loop over the same range but only print even numbers using continue.
• Create a list of salaries. Use a loop to print only those above 50000.
• Use a list comprehension to create a list of the squares of numbers 1 to 8.