The pi is a mathematical constant whose value is 3.14159, which is used in calculations involving circles, spheres, periodic phenomena, and converting from degrees to radians.

Here are two ways to use pi in Python:

1. Using math.pi
2. Using numpy.pi

import numpy as np
import math

print(math.pi)
# Output: 3.141592653589793

print(np.pi)
# Output: 3.141592653589793

Area of a Circle

The basic application of math.pi is to calculate the area of a circle.

The basic formula for calculating the circle’s area is A = π r².

import math

radius = 5

area = math.pi * radius ** 2

print("Area:", area)

# Output: Area: 78.53981633974483

Converting Degrees to Radians

You can use the pi when you want to convert degrees to radians (radians = degrees * (π/180)).

import math


def degrees_to_radians(degrees):
    return degrees * (math.pi / 180)


print(degrees_to_radians(90))

# Output: 1.5707963267948966 (π/2)

print(math.sin(degrees_to_radians(90)))

# Output: 1.0

Numerical computations with NumPy

Let’s calculate the vectorized circle area calculation.

import numpy as np

array_of_radius = np.array([1, 2, 3])

area = np.pi * array_of_radius ** 2

print("Area:", area)

# Output: [ 3.14159265 12.56637061 28.27433388]

The output is also an array of area values of the respective input radius.