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math.factorial() method with example in Python

Python math.factorial() method: Here, we are going to learn about the math.factorial() method with example in Python. By IncludeHelp Last updated : September 19, 2023

Python math.factorial() method

The math.factorial() method is a library method of math module, it is used to find the factorial of a given number, it accepts a positive integer number and returns the factorial of the number.

Syntax

Syntax of math.factorial() method is:

math.factorial(n)

Parameter(s):

The following are the parameter(s) of math.factorial() method is:

• n – a positive integer number.

Return value

int – it returns factorial of given number n.

Example

Consider the below example with sample input and output:

Input:
a = 6

# function call
print(math.factorial(a))

Output:
720

Python program to demonstrate the example of math.factorial() method

# Python code to demonstrate example of 
# math.factorial() method

# importing math module
import math

# numbers
a = 0
b = 1
c = 6
d = 13

# printing factorial
print("factorial of ", a, " is = ", math.factorial(a))
print("factorial of ", b, " is = ", math.factorial(b))
print("factorial of ", c, " is = ", math.factorial(c))
print("factorial of ", d, " is = ", math.factorial(d))

Output

factorial of  0  is =  1
factorial of  1  is =  1
factorial of  6  is =  720
factorial of  13  is =  6227020800

ValueError: factorial() not defined for negative values

If we try to find the factorial of a negative integer value – method will return this error.

# Python code to demonstrate example of 
# math.factorial() method

# importing math module
import math

# -ve integer 
a = -5

print(math.factorial(a))

Output

Traceback (most recent call last):
  File "/home/main.py", line 10, in <module>
    print(math.factorial(a))
ValueError: factorial() not defined for negative values

ValueError: factorial() only accepts integral values

If we try to find the factorial of a float value – method will return this error.

# Python code to demonstrate example of 
# math.factorial() method

# importing math module
import math

# -ve integer 
a = 5.1

print(math.factorial(a))

Output

Traceback (most recent call last):
  File "/home/main.py", line 10, in <module>
    print(math.factorial(a))
ValueError: factorial() only accepts integral values