Python while Loop

Loop Satellite

While Loops

Use `while` when you don't know the number of iterations in advance.

See patternsAvoid infinite loops

Patterns

# Process until empty
while queue:
    job = queue.pop(0)
    handle(job)

# Read until end of input
while True:
    data = stream.read()
    if not data:
        break
    process(data)

# Countdown
count = 5
while count > 0:
    print(count)
    count -= 1

while/else

The else clause runs when the condition becomes False (not on break):

attempts = 3
while attempts > 0:
    if try_connect():
        break
    attempts -= 1
else:
    print("All attempts failed")

Tips

• Always ensure the loop condition eventually becomes False.
• Use break to exit sentinel loops.
• Use time.sleep(interval) in polling loops to avoid busy-waiting.
• Prefer for loops when iterating over a known sequence.

Next up in your learning path

For loops

Prefer for loops when iterables have known length.

Companion

Loop control statements

Practice break, continue, pass, and loop else patterns.

Technique

Nested loops

Handle combinations and grids responsibly.

Advanced