Python Basics · Control Flow · Lesson 9 of 36
for Loops and range()
Concept
for Loops and range()
for loops in Python iterate directly over sequences. range() generates a sequence of numbers to loop over.
range(5) generates 0 through 4, not 0 through 5 — it always stops one short of its argument, which is the most common range() surprise for beginners.
By the end of this lesson
- Explain the core idea behind for Loops and range().
- Predict output before running a change.
- Test one realistic and one unusual input.
- Use the result to make the next decision.
How to study this page
- 1. Read one concept.
- 2. Change the example.
- 3. Run, compare, and explain.
- 4. Complete the challenge below.
Syntax
for variable in range(start, stop, step):
# coderange with a start and step
for i in range(2, 10, 2):
print(i)Note: range(2, 10, 2) starts at 2, stops before 10, and steps by 2 each time.
Self-check before continuing
Without looking at the example, describe what changes when you modify one input in for Loops and range(). Then reopen the editor and prove your explanation with a small test.
You are ready to continue when you can predict, test, and explain the result.
Your turn
Use a for loop with range() to print the numbers 1 through 10.
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Console