Lesson 15 of 55
8 mins readPython Numeric for Loops (start, stop, step)
In Plain English
The numeric `for` loop iterates a control variable from `start` to `stop` by an optional `step` increment. The loop variable is automatically local to the loop body.
Deep Dive: How It Works
Syntax: `for var = start, stop [, step] do ... end`.
Default Step: If step is omitted, Lua increments by 1.
Negative Step: `for i = 10, 1, -2 do` steps backwards.
Automatic Local: The iterator `var` is implicitly declared local and cannot be modified directly.
Core Rules to Remember
3-Part Numeric for: `for i = 1, 10, 2 do` iterates 1, 3, 5, 7, 9.
Read-Only Iterator: Never mutate the loop index variable inside the loop body.
Live Interactive Example
Hit Run Code to see it liveForward and Reverse Numeric Loops
Python 3.12
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Output Console
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How it works: Numeric for executed with positive step 2 and negative step -1.
Your Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Micro Exercise
Sum Range with Numeric for
- Declare `local total = 0`.
- Use `for i = 1, 5 do total = total + i end`.
- Print `"Sum: " .. total`.
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Sandbox Output
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