Python math.factorial() – Factorial Function

Python math.factorial()

math.factorial(x) function returns the factorial of x as an integer.

Syntax

The syntax to call factorial() function is

math.factorial(x)

where

Parameter	Required	Description
x	Yes	An integer value. x >= 0.

Note: Since Python v3.9, factorial() does not accept floats with integral values like 5.0.

If x is not integral value, then factorial(x) raises ValueError.

Examples

1. Find factorial of integer

In the following program, we shall read an integer from user, and find its factorial.

Python Program

import math

x = int(input('Enter an integer : '))
result = math.factorial(x)
print('Factorial :', result)

Output #1

Enter an integer : 5
Factorial : 120

Output #2

Enter an integer : 0
Factorial : 1

Output #3

Enter an integer : -4
Traceback (most recent call last):
  File "/Users/pe/Desktop/Projects/Python/example.py", line 4, in <module>
    result = math.factorial(x)
ValueError: factorial() not defined for negative values

2. Find factorial of integer online

You can run the following program online and find the factorial of a number.

Python Program

import math

x = 7
result = math.factorial(x)
print('Factorial :', result)

Run Code Online

Summary

In this Python Math tutorial, we learned the syntax of, and examples for math.factorial() function.