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

First, let’s see **What is Circumference of Circle?**

The perimeter is the curve length around any closed figure.

**Formula:**

Circumference of Circle: C = 2 * pi * r Where, r = Radius of circle pi = pi is geek letter which is a constant whose approximate value is 3.14159.. or 22/7 .

**Examples:**

Input:Radius = 5

Output:The circumference of the circle is 31.40.

Input:Radius = 2

Output:The circumference of the circle is 12.56.

Let’s see the program for this:

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

# define a function for # calculating circumference # of a circle def circumference_circle(r): # constant value PI = 3.14 # printing the radius print("Radius =",r) # calculating the circumference C = 2 * PI * r # printing the circumference print("The circumference of the circle is", C) # main code if __name__ == "__main__" : # input radius radius = 5 # function calling circumference_circle(radius)

**Output:**

Radius = 5 The circumference of the circle is 31.400000000000002

**Code Version 2:** Create a user-defined function that will calculate and print the circumference 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 # define a function for # calculating circumference # of a circle def circumference_circle(r): # printing the radius print("Radius =",r) # calculating the circumference C = 2 * pi * r # printing the circumference print("The circumference of the circle is", C) # main code if __name__ == "__main__" : # input radius radius = 2 # function calling circumference_circle(radius)

**Output:**

Radius = 2 The circumference of the circle is 12.566370614359172

**Code version 3:** Create a user-defined one-line anonymous function which will calculate and return the circumference of a circle using a **lambda** statement.

# including pi constant # from the math library # into this program from math import pi # main code if __name__ == "__main__" : # input radius radius = 2 # printing the radius print("Radius =", radius) # create a one line function # using lambda statement # for calculating # circumference of a # circle circumference_circle = lambda r : 2 * pi * r # function calling print("The circumference of the circle is", circumference_circle(radius))

**Output:**

Radius = 2 The circumference of the circle is 12.566370614359172