Python Loops

Loops repeat code. They are essential for handling collections and repeating tasks.

Two main loop types:

• for: repeat over items (lists, ranges)
• while: repeat until a condition becomes false

for loop (over a list)

cities = ["Boston", "Portland", "Atlanta"]

for city in cities:
    print(city)

Expected output:

Boston
Portland
Atlanta

for loop with range()

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

Expected output:

0
1
2
3
4

while loop (repeat until condition changes)

count = 0

while count < 3:
    print(count)
    count += 1

Expected output:

0
1
2

break and continue

break stops the loop:

for i in range(6):
    if i == 3:
        break
    print(i)

Expected output:

0
1
2

continue skips one iteration:

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

Expected output:

0
1
3
4

Graph: loop cycle

flowchart TD
  A[Start] --> B{Condition/Items left?}
  B -->|Yes| C[Run body]
  C --> D[Update / next item]
  D --> B
  B -->|No| E[Exit]

In the next lesson, you will learn functions so your code becomes reusable and easier to maintain.