Python · Quick Reference

Lesson 7 — Loops Cheat Sheet

Python

In one line: Loops let your program repeat a block of code without you having to write it multiple times. Python has exactly two loop types — each suited to different situations.

Key Ideas

1Two Types of Loops. Loops let your program repeat a block of code without you having to write it multiple times. Python has exactly two loop types — each suited to different situations.

2The for Loop. A for loop steps through each item in a sequence one by one, assigning it to a variable you name. When the sequence is exhausted, the loop ends automatically.

3The while Loop. A while loop repeats its body as long as its condition remains True. The condition is checked before each iteration — if it's already False at the start, the body neve...

4Loop Control — break, continue, pass. Three special keywords give you fine-grained control over loop execution.

5enumerate() & zip(). Two built-in functions that make for loops dramatically more powerful and Pythonic — eliminating the need for manual counter variables.

Code Examples

# Looping over a list
fruits = ["apple", "banana", "mango"]
for fruit in fruits:
    print(f"I like {fruit}")
# I like apple
# I like banana
# I like mango

# Looping over a string (character by character)
for char in "Python":
    print(char, end="-")     ...

# Print 1 to 5
for i in range(1, 6):
    print(i, end=" ")   # 1 2 3 4 5
print()

# Countdown from 5
for i in range(5, 0, -1):
    print(i, end=" ")   # 5 4 3 2 1
print("🚀")

# Sum of 1 to 100
total = 0
for n in range(1, 101):
    total += n
print(total)  ...

# Basic while
count = 1
while count 5:
    print(count, end=" ")
    count += 1         # ← MUST update or infinite loop!
# 1 2 3 4 5

# Keep asking until valid input — very common pattern
age = -1
while age 0 or age > 120:
    age = int(input("Enter val...