Python Program to Find Area of a Circle

In this tutorial, we will learn how to find the area of a circle using the Python programing language. Previously, we saw how to find the area of a square, we will follow a similar approach and use the formula for calculating the area of a circle.

Formula:

Our program should take input as follows and display area as output.

For a circle with a radius of 7 cm, the area of a circle is 154cm

Input- Radius: 7

Output- Area: 154

Look at the algorithm below to understand the working.

Algorithm

Step 1- Define a function area_of_circle()

Step 2- Set pi as constant and initialize to 3.147

Step 3- Declare variable area to calculate and store area

Step 4- Return area

Step 5- Take input of radius from the user

Step 6- Pass radius in the function

Step 7- Print the result

Python Program

Look at the program to understand the implementation of the above-mentioned approach.

def area_of_circle(r):
    pi=3.147
    area= pi*r*r
    return area

radius=float(input("Enter Radius: "))
print("Area: ",area_of_circle(radius))

Enter Radius: 3.2
Area: 32.22528

To calculate area, we can also use the pow() function which is a function in the math class of the Python library.

The pow(x,y) returns the value of x raised to the power y.

In place of pi*r*r in #line 8 of the code, we can also write pi*pow(r,2) to calculate area.

To know about Python math library functions in detail check out this article.

Conclusion

So far, we have learned how to define a function to calculate the area of a circle where the radius is given by the user in Python. In the function body, we have set pi as a constant value and put it in the formula along with the radius to calculate the area. Finally, the area was returned by the function and displayed using the print() function.