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# Factorial of a number in python

A non-negative integer’s factorial is the multiplication of all integers less than or equal to n.

``````n = int(input("Enter a number: "))
fact = 1
if n < 0:
print(" Factorial does not exist for negative numbers")
elif n == 0:
print("The factorial of 0 is 1")
else:
for i in range(1,n + 1):
fact = fact*i
print("The factorial of",n ,"is",fact)    ``````

Output:

Enter a number: 9

The factorial of 9 is 362880

Contents

#### Using Recursion

``````def factorial(num):
return 1 if (num==1 or num==0) else num * factorial(num - 1);

n = int(input("Enter a number: "))
print("Factorial of",n,"is", factorial(n))  ``````

Output:

Enter a number: 7

Factorial of 7 is 5040

#### Using built-in function

Math module includes the build-in factorial() method.

``````import math
def factorial(num):
return(math.factorial(num))
n = int(input("Enter the number:"))
fact = factorial(n)
print("Factorial of", n, "is", fact)  ``````

Output:

Enter the number: 6

Factorial of 6 is 720