Control FlowLesson 8 of 1913 min
while Loops, break, and continue
Repeat for as long as a condition holds — and stay out of infinite loops.
By the end you will be able to
- Write a while loop with a condition that eventually becomes False
- Exit early with break and skip an iteration with continue
- Recognise and avoid infinite loops
Use for when you know what to loop over. Use while when you only know when to stop.
A while loop rechecks its condition before every pass and keeps going while it is truthy.
Python
Output
3
2
1
Liftoff!
— expected output; press Run to execute it yourselfbreak and continue
breakleaves the loop immediatelycontinueskips the rest of this pass and jumps to the next one
Both work in for loops too.
Python
Output
First multiple of 3: 9
1 3 5 7 9
— expected output; press Run to execute it yourselfA processing queue
while shines when the collection shrinks or grows as you work through it.
Python
Output
Running render... 3 left
Running compress... 2 left
Running upload... 1 left
Running notify... 0 left
Queue empty.
— expected output; press Run to execute it yourselfExercise
Write a function digit_count(n) that returns how many digits a positive integer has, using a while loop and //. digit_count(4071) should return 4.
Python
Output
Press Run to execute this code.
Check your understanding
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