Lesson 13 of 55
8 mins readPython While & Until Loops
In Plain English
`while` loops repeat a block as long as the condition evaluates to true. `until` is the clean inverted equivalent, looping until the condition becomes true.
Deep Dive: How It Works
while Loop: Tests condition at the top; continues while truthy.
until Loop: Repeats until condition becomes truthy (equivalent to while not condition).
Infinite Loops: `while (1) { ... }` runs indefinitely until explicitly broken with `last`.
Core Rules to Remember
while Loop: Repeats as long as condition evaluates to true.
until Loop: Repeats until condition evaluates to true.
Live Interactive Example
Hit Run Code to see it liveCounting with while and until
Python 3.12
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Output Console
Click "Run Code" to view the rendered output.
How it works: while counted up to 3; until terminated once $countdown equaled 0.
Your Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Micro Exercise
Generate Power Sequence with while
- Set `my $val = 1;`
- Use a `while ($val <= 8)` loop to print `"$val "` and double `$val *= 2;` each iteration.
- Print `"\n"` after the loop.
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Sandbox Output
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