factorial() in Python

Not many people know, but python offers a direct function that can compute the factorial of a number without writing the whole code for computing factorial.

Naive method to compute factorial

The factorial of 23 is : 25852016738884976640000

Time Complexity: O(n)
Auxiliary Space: O(1)

Using math.factorial()

This method is defined in “math” module of python. Because it has C type internal implementation, it is fast.

math.factorial(x)
Parameters :
x : The number whose factorial has to be computed.
Return value :
Returns the factorial of desired number.
Exceptions : 
Raises Value error if number is negative or non-integral.

The factorial of 23 is : 25852016738884976640000

Time Complexity: O(n)
Auxiliary Space: O(1)

Exceptions in math.factorial()

• If given number is Negative : 

Output:

Traceback (most recent call last):
  File "/home/f29a45b132fac802d76b5817dfaeb137.py", line 9, in 
    print (math.factorial(-5))
ValueError: factorial() not defined for negative values

• If given number is Non – Integral Value : 

Output:

Traceback (most recent call last):
  File "/home/3987966b8ca9cbde2904ad47dfdec124.py", line 9, in 
    print (math.factorial(5.6))
ValueError: factorial() only accepts integral values

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