How to Find Area of a Circle with Diameter in Python | Functions

How to find area of a circle with diameter in Python using functions.

In this article, you will learn how to find area of a circle with diameter in Python using functions.

Example

Standard Formula

You should have knowledge of the following topics in Python programming to understand this program:

• Python input() function

1. By using the default value of PI = 3.14

# How to Find Area of a Circle with Diameter in Python
print("Enter the radius of the circle::\n")

r, d, c, a = float(input()), None, None, None
# r = radius, d = diameter, c = circumference, a = area

# It will calculate the diameter, circumference, and area
d = 2 * r
c = 2 * 3.14 * r
a = 3.14 * (r * r)

# It will print the final output
print("Diameter       = ", d, "units")
print("Circumference  = ", c, "units")
print("Area           = ", a, " sq. units")

Run

Output

Explanation

In the above program, we have taken input 10 from the user via the system console. Then we applied the standard formula to calculate the diameter, circumference, and area.

Standard formulas are given at the top of the article near the example portion can see there.

After the whole calculation, It will return these values following: 

• Diameter = 20.0 units
• Circumference = 62.800000000000004 units
• Area = 314.0 sq. units

2. By using Math.PI constant

# How to Find Area of a Circle with Diameter in Python using math.pi constant
# Import math Library
import math

print("Enter the radius of the circle::\n")

r, d, c, a = float(input()), None, None, None
# r = radius, d = diameter, c = circumference, a = area

# It will calculate the diameter, circumference, and area
d = 2 * r
c = 2 * math.pi * r
a = math.pi * (r * r)

# It will print the final output
print("Diameter       = ", d, "units")
print("Circumference  = ", c, "units")
print("Area           = ", a, " sq. units")

Run

Output

How to Find Area of a Circle with Diameter in Python using Functions

# How to Find Area of a Circle with Diameter in Python using Functions
# To calculate the diameter
def Diameter(r):
    return 2 * r

# To calculate the circumference
def Circumference(r):
    return 2 * 3.14 * r

# To calculate the area
def Area(r):
    return 3.14 * (r * r)

# It's the driver code
print("Enter the radius of the circle::\n")

r = float(input()) # r = radius

# It will print the final output
print("Diameter       = ", Diameter(r), "units")
print("Circumference  = ", Circumference(r), "units")
print("Area           = ", Area(r), " sq. units")

Run