Python Program to Find Factorial of a Number Using While Loop

Before going to the program first let us understand what is a Factorial of a Number?

Factorial of a Number:

                  The factorial of a Number n, denoted by n! is the product of all positive integers less than or equal to n.

The value of 0! is 1 according to the convention for an empty product.

For example,

5! = 5 * 4 * 3 * 2 * 1 = 120

Program code for Factorial of a Number in Python:

# Python program to find the factorial of a number

#Define a factorial and loop variable
fact = 1
i = 1

# To take input from the user
num = int(input("Enter a number: "))

# check if the number is negative or positive
if num < 0:
    print("Sorry, factorial does not exist for negative numbers")
    while i <= num:
        fact = fact*i
        i = i + 1
    print("The factorial of", num, "is", fact)

Related: Python Program to Find Factorial of a Number Using For Loop


  • First, the computer reads the number to find the factorial of the number from the user.
  • Then using a while loop the value of ‘i’ is multiplied by the value of ‘fact’.
  • The loop continues till the value of ‘num’. Finally, the factorial value of the given number is printed.


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