Explanation

The factorial of a number is the product of all the integers from 1 to that number.

For example, the factorial of 6 (denoted as 6!) is 12345*6 = 720. Factorial is not defined for negative numbers and the factorial of zero is one, 0! = 1.

if the no entered by the user is greater then 0 then for loop will iterate n times, for loop along with the range() function is used.

The arguments inside range function is (1, n+1) meaning, greater than or equal to 1 and less than n+1 (meaning n+1).n+1 is used as python excludes last element.

Code:-

num = int(input("Enter a number: "))
factorial = 1
# check if the number is negative, positive or zero
if num < 0:
    print("Sorry, factorial does not exist for negative numbers")
elif num == 0:
    print("The factorial of 0 is 1")
else:
    for i in range(1,num + 1):
        factorial=factorial*i
    print("The factorial of",num,"is",factorial)

Output:-

Using Recursion

#Function to return the factorial of a number using recursion
def factorial(num):
    factorial = 1
# check if the number is negative, positive or zero
    if num < 0:
        print("Sorry, factorial does not exist for negative numbers")
    elif num == 0:
        print("The factorial of 0 is 1")
    else:
        for i in range(1,num + 1):
            factorial=factorial*i
        print("The factorial of",num,"is",factorial)

num = int(input("Enter a number: "))
factorial(num)