The range() Function

Generate sequences of numbers with range()

The range() Function — Counting in a Loop

What Is range()?

range() generates a sequence of numbers — perfect for when you need to repeat something a specific number of times, or count through a range of numbers.

Syntax

python

for i in range(5):
    print(i)          # 0, 1, 2, 3, 4

for i in range(2, 6):
    print(i)          # 2, 3, 4, 5

for i in range(0, 10, 2):
    print(i)          # 0, 2, 4, 6, 8

Call	Generates
`range(stop)`	0, 1, 2, ..., stop-1
`range(start, stop)`	start, start+1, ..., stop-1
`range(start, stop, step)`	start, start+step, start+2*step, ...

How It Works

python

for i in range(3):
    print(f"Round {i + 1}")

Output:

Round 1
Round 2
Round 3

Step by step:

`range(3)` creates the sequence `[0, 1, 2]`

First iteration: `i = 0`, prints "Round 1"

Second iteration: `i = 1`, prints "Round 2"

Third iteration: `i = 2`, prints "Round 3"

No more items — loop ends

� **Why start at 0?** Python (like most languages) starts counting from 0. If you want to count from 1, just add 1 inside the loop: `i + 1`.

Common Patterns with range

python

# Count from 1 to 5
for i in range(1, 6):
    print(i)          # 1, 2, 3, 4, 5

# Count backward
for i in range(10, 0, -1):
    print(i)          # 10, 9, 8, ..., 1
print("Blast off! 🚀")

# Use i to access list items by index
colors = ["red", "green", "blue"]
for i in range(len(colors)):
    print(f"Color {i}: {colors[i]}")

� **Key insight:** Use `for item in list:` when you want each value. Use `for i in range(len(list)):` when you also need the index.

Why Use range()?

**Repeat N times** — `for _ in range(10): print("Hello")`

**Number sequences** — `for year in range(2000, 2026):`

**Index-based access** — combined with `len()` to process lists by position

**Countdowns** — `range(10, 0, -1)` for rocket launches

**Stepping** — `range(0, 100, 5)` for multiples of 5

Common Mistakes

❌ Wrong	Why	✅ Right
`range(5)` expecting `1, 2, 3, 4, 5`	Starts at 0 by default	`range(1, 6)`
`range(1, 5)` expecting 5 items	Stop is exclusive — only 1, 2, 3, 4	`range(1, 6)`
`range(10, 0)`	Start < stop with default step=1 = empty	`range(10, 0, -1)`
`for i in range(len(list)):` when values alone suffice	Overly complex	`for item in list:`

Your Turn!

Write a program that:

Uses `range()` to print numbers from 1 to 10

Then uses `range()` to print **only the even numbers** from 2 to 20

Then uses `range()` with a step to print multiples of 5 from 5 to 50

💡Need a hint? (3 available)

#1range(stop) starts at 0 by default

#2range(start, stop) — stop is exclusive

#3range(start, stop, step) — step controls how much to jump

🔑Show solution (try it yourself first!)

print("1 to 10:")
for i in range(1, 11):
    print(i)

print("Even numbers 2-20:")
for i in range(2, 21, 2):
    print(i)

print("Multiples of 5:")
for i in range(5, 51, 5):
    print(i)

✏️ Code Editor

Loading Python...

📤 Output

Write your solution and click "Run Code" to test it!

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