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Python Program to Find the Factorial of a Number

What is factorial?

Factorial is a non-negative integer. It is the product of all positive integers less than or equal to that number you ask for factorial. It is denoted by an exclamation sign (!).


The factorial value of 4 is 24.

Note: The factorial value of 0 is 1 always. (Rule violation)

Example -


Enter a number: 10
The factorial of 10 is 3628800

Explanation -

In the above example, we have declared a num variable that takes an integer as an input from the user. We declared a variable factorial and assigned 1. Then, we checked if the user enters the number less than one, then it returns the factorial does not exist for a negative number. If it returns false, then we check num is equal to zero, it returns false the control transfers to the else statement and prints the factorial of a given number.

Using Recursion

Python recursion is a method which calls itself. Let's understand the following example.

Example -


Factorial of 5 is 120

Explanation -

In the above code, we have used the recursion to find the factorial of a given number. We have defined the fact(num) function, which returns one if the entered value is 1 or 0 otherwise until we get the factorial of a given number.

Using built-in function

We will use the math module, which provides the built-in factorial() method. Let's understand the following example.

Example -


Enter the number: 6
Factorial of 6 is 720

We have imported the math module that has factorial() function. It takes an integer number to calculate the factorial. We don't need to use logic.

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