In this post, we will write a program for how to calculate the area of a circle in python.

First, letâ€™s see **What is the Area of Circle?**

The area enclosed by a circle of radius r in 2-dimensional plane.

**Formula:**

Area of circle: A = pi * r * r Or pi * r^{2}Where, r = Radius of circle pi = pi is geek letter which is a constant whose approximate value is 3.14159...

**Examples:**

Input: Radius = 7

Output: The area of the circle is 154.0Input: Radius = 2

Output: The area of the circle is 12.56

Letâ€™s see the program for this:

**Code Version 1:** Create a user-defined function that will calculate and print the area of a circle.

# define a function for # finding area of a circle def area(r): # constant value of PI PI = 22/7 # printing the radius print("Radius =", r) # calculating the area area = PI * (r * r) # printing the area print("The area of the circle is", area) # main code if __name__ == "__main__" : # input radius radius = 7 # function calling area(radius)

**Output:**

Radius = 7 The area of the circle is 154.0

**Code Version 2:** Create a user-defined function that will calculate and print the area of a circle. In this code version, we are using **pi **constant value which is directly taken from the **math** library.

# including pi constant # from the math library # into this program from math import pi # defina a function for # finding area of circle def area(r): # printing the radius print("Radius =", r) # calculating the area area = pi * (r * r) # printing the area print("The area of the circle is", area) # main code if __name__ == "__main__" : # input radius radius = 7 # function calling area(radius)

**Output:**

Radius = 7 The area of the circle is 153.93804002589985