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

ParameterRequiredDescription
xYesAn 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

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

Summary

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