How to Represent an Infinite Number in Python

John on May 05, 2022

Infinity is an abstract number that can be negative or positive and represents both the small and largest possible number. In this tutorial, we will go through some of the different ways to use infinity in Python.

Create Positive and Negative Infinity in Python Using float()

In Python, like many other popular programming languages, infinity is represented with the keyword inf. To create infinity in Python pass 'inf' or '-inf' for negative as the first argument of the float() function like this:

#Positive infinity
infinity = float('inf')
print('Positive Infinity: ', infinity)

#Negative infinity
neg_infinity = float('-inf')
print('Negative Infinity: ', neg_infinity)

Positive Infinity:  inf
Negative Infinity:  -inf

Use the math Package to Represent Positive and Negative Infinity in Python

Another way to create negative and positive infinity in Python is with the math package. Use the math.inf property for positive infinity and -math.inf for negative infinity.

#Positive infinity
infinity = float('inf')
print('Positive Infinity: ', infinity)

#Negative infinity
neg_infinity = float('-inf')
print('Negative Infinity: ', neg_infinity)

Positive Infinity:  inf
Negative Infinity:  -inf

Check Number is Infinity in Python

To check a number is infinite in Python use the isinf function from the math package like this:

import math

#Positive infinity
infinity = math.inf
print('Positive Infinity: ', math.isinf(infinity))

#Negative infinity
neg_infinity = -math.inf
print('Negative Infinity: ', math.isinf(neg_infinity))

Represent Positive and Negative Infinity Using NumPy

To represent infinity using NumPy, use np.inf or -np.inf:

import numpy as np

#Positive infinity
infinity = np.inf
print('Positive Infinity: ', infinity)

#Negative infinity
neg_infinity = -np.inf
print('Negative Infinity: ', neg_infinity)

Positive Infinity:  inf
Negative Infinity:  -inf

Represent Positive and Negative Infinity Using the Decimal Package

If you're using the Python decimal package you can represent negative and positive infinity with it like this:

import math
from decimal import Decimal

#Positive infinity
infinity = Decimal('Infinity')

#Negative infinity
neg_infinity = Decimal('-Infinity')

print('Positive Infinity: ', infinity)
print('Is Infinity: ', math.isinf(infinity))
print('Negative Infinity: ', neg_infinity)
print('Is Infinity: ', math.isinf(neg_infinity))

Positive Infinity:  Infinity
Is Infinity:  True
Negative Infinity:  -Infinity
Is Infinity:  True