While loops and loop control
A for loop follows a set of values. A while loop keeps going for as long as its condition remains true. That flexibility is powerful — and requires careful thought about when the loop ends.
A while loop checks its condition first
while count < 4: tests the condition before every iteration. When it becomes false, execution continues after the loop. If it starts false, the body does not run at all.
The body generally needs to change the state used by the condition. Without that change, a condition that starts true may stay true forever.
Design the exit before the loop
Before running a loop, write down its stopping condition. Then confirm which statement causes progress towards that condition. In a counter loop, increment count on every normal pass.
This matters especially when continue is involved: it jumps to the next check and skips any code that follows it in the loop body. Moving the increment below a continue can accidentally create a loop that never advances.
break and continue have distinct jobs
break leaves the nearest enclosing loop immediately. continue skips the rest of the current iteration and moves to the next one. Neither leaves the entire function; they affect only the loop.
Use break for a clear early exit, such as finding the first matching item. Use continue for a value you want to ignore, while making sure state still progresses correctly.
Choose the simplest loop that works
If you already have a collection of items, for item in items is usually easier to read than managing an index with while. Choose while when the number of repetitions depends on a condition that changes dynamically.
For demonstrations, use small fixed limits and known exit conditions. The browser playground can stop a runaway execution, but a timeout is a safety mechanism, not a substitute for correct loop design.
Try it yourself.
Choose a starting example or write something completely different. You control the code; the Run button executes what is in the editor, not a hidden preset.
Decrease a counter until the condition is false.
Press Run Python to execute the editable code.
Begin with remaining = 0. Why does the body not run?
Need a hint?
while checks the condition before its first iteration.
On first Run, a pinned Python runtime downloads from jsDelivr. Code executes locally in your browser's Web Worker, not on our server. It cannot inspect your normal PC files or Windows hardware. Avoid entering secrets. Heavy/infinite loops are stopped by a time limit.
Check your understanding.
Try answering each question before opening its reference answer. Explain the idea aloud or change an example to test it for yourself.
Why might a
whileloop run forever even when it contains acontinuestatement?View answer
continueskips all remaining statements in the current iteration. If a counter increment or state update sits after it, the loop may keep returning to the same unchanged condition and never reach its stopping point. Put the progress update before paths that continue, and reason about every branch.What is the difference between
breakandcontinue?View answer
breakleaves the nearest enclosing loop immediately, so execution resumes after that loop.continuedoes not exit the loop: it skips the rest of the current iteration and starts the next condition check or next item. Use them intentionally and keep the loop’s exit condition clear.
Where this leads.
Loops become more useful when we can hold several related values together in one collection.