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Day 8 — Python while loops, break and continue
A for loop runs a known number of times. A while loop runs until something becomes true — which is powerful, and easy to get wrong.
while
The one real danger
Forget
Every
count += 1 and the condition never becomes false — the loop runs forever. This playground stops after a while and tells you; a real program would just hang.
Every
while needs something inside it that moves towards the exit.A countdown
break — leave the loop early
continue — skip this one, carry on
for or while?
- for — you know what you are looping over: a list, a range, rows of data. This is what you will use 95% of the time.
- while — you are waiting for a condition: a balance reaching zero, a retry succeeding, input being valid.
A worked example
How many months until savings reach a target?
Try these yourself
- Count down from 10 to 1 with a while loop.
- Use break to stop at the first negative number in a list.
- Use continue to skip empty strings while printing a list of names.
- Work out how many months at 8000 it takes to reach 50000.
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