Numbers and math

In plain English

Python has two main number types: int for whole numbers and float for decimal numbers. Operators like +, -, *, /, // and % do arithmetic, and / always returns a float. round() trims a number to a set number of decimal places. The math module (reached with import math) adds helpers such as sqrt for square roots.

Step by step

1. 1Use int for whole numbers and float for decimals.
2. 2Use / for true division and // to drop the remainder.
3. 3Trim decimals with round(value, places).
4. 4Import math to reach functions like sqrt and floor.

import math

apples = 7
price = 3.14159

print(apples + 2)
print(apples / 2)
print(apples // 2)
print(apples % 2)

print(round(price, 2))
print(round(0.1 + 0.2, 2))
print(math.sqrt(16))
print(math.floor(price))

Common mistakes

• Using / when you want whole-number division and being surprised by the .0 result.
• Treating 0.1 + 0.2 as exactly 0.3 instead of rounding it for display.
• Calling math.sqrt without import math first.
• Confusing % (the remainder) with division.