Area of a circle program in Python

The area of a circle is π × r², where r is the radius. Python's math module has an accurate value of π.

The program

import math

radius = float(input("Radius: "))

area = math.pi * radius ** 2
circumference = 2 * math.pi * radius

print(f"Area = {area:.2f}")
print(f"Circumference = {circumference:.2f}")

Typed in this example: 5. Press Run to type your own.

Radius: 5
Area = 78.54
Circumference = 31.42

How it works

• import math gives you access to the math module, which comes with Python. math.pi is 3.141592653589793.
• radius ** 2 squares the radius. ** is done before *, so this is π × (r²), as the formula needs.
• :.2f inside the f-string rounds the printed number to 2 decimal places. The variable itself keeps its full value.