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
Python3
# Python code to demonstrate naive method# to compute factorialn = 23fact = 1for i in range(1, n+1): fact = fact * iprint("The factorial of 23 is : ", end="")print(fact) |
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.
Python3
# Python code to demonstrate math.factorial()import mathprint("The factorial of 23 is : ", end="")print(math.factorial(23)) |
The factorial of 23 is : 25852016738884976640000
Time Complexity: O(n)
Auxiliary Space: O(1)
Exceptions in math.factorial()
- If given number is Negative :
Python3
# Python code to demonstrate math.factorial()# Exceptions ( negative number )import mathprint("The factorial of -5 is : ", end="")# raises exceptionprint(math.factorial(-5)) |
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 :
Python3
# Python code to demonstrate math.factorial()# Exceptions ( Non-Integral number )import mathprint("The factorial of 5.6 is : ", end="")# raises exceptionprint(math.factorial(5.6)) |
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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