**Factorial recursion** is a method in which a function directly or indirectly calls itself. In mathematics, Factorial means the product of all the positive integers from 1 to that number. An exclamation mark is used after the integer to show that it’s a factorial.

For example, factorial eight is 8! So, it means multiplication of all the integers from 8 to 1 that equals 40320. Factorial of zero is 1. We can find a factorial of a number using python. There are various ways of finding; The Factorial of a number in python. Among which recursion is the most commonly used.

## Factorial Function in Python

**Source Code: Python Program to find factorial of a number using recursive function**

def recursive_factorial(n): if n == 1: return n else: return n*recursive_factorial(n-1) #function calling itself #taking input from the user number = int(input("User Input : ")) print("The factorial of", number, "is", recursive_factorial(number))

**Output :**

User Input: 4 The factorial of 4 is 24

**Source code: Displaying an error message if a user inputs a negative integer**

def recursive_factorial(n): if n == 1: return n else: return n*recursive_factorial(n-1) #taking input from the user number = int(input("User input : ")) # If the user input negative integer if number < 0: print("Bad Input") else: print("The factorial of", number, "is", recursive_factorial(number))

**Output:**

User input : -1 Bad Input

**Source code: Factorial of zero is 1.**

def recursive_factorial(n): if n == 1: return n else: return n*recursive_factorial(n-1) #taking input from the user number = int(input("User Input : ") # If the user input negative integer if number < 0: print("Bad Input") # If the user inputs 0 elif number == 0: print("The factorial of 0 is 1") else: print("The factorial of", number, "is", recursive_factorial(number))

**Output:**

User Input : 0 The factorial of 0 is 1

**FAQs on Factorial Recursion**

**What is Factorial recursion?**

Factorial of a positive integer is the multiplication of all integers from that number to 1.

Factorial is represented by an exclamation mark.

If the user inputs a number let’s assume the number is n, so n factorial is n! = n * (n-1)!

For example:

factorial of 3 is

3! = 3 * 2 * 1. which equals 6.

There is no factorial output for negative integers

So, the factorial of 0 is 1

**How does Factorial recursion work?**

Factorial of a number is the multiplication of all the integers from that number to 1.

The input value (positive integer) is passed; as a parameter to the factorial function.

So, Whenever the function runs, It multiplies the value of a parameter and recursively calls the function itself while decrementing the parameter value by 1.

Once the value becomes 0 the function returns 1 (as the factorial of 0 is 1) and returns the multiplier value that is the factorial of an inputted number.

**How do you find the Recursive Factorial?**

Factorial recursion is a function that is defined in such a way that it calls itself. Until it returns the factorial of the number passed as a parameter to the function.

Formula to calculate Factorial recursion.

n!=n * (n-1)! also [n!=1 if n=0]

factorial of 0 is 1

There is no factorial output for negative integers.

**What is recursion? Write a program for factorial calculation.**

Recursion is a concept where you can loop through data to get a result. A problematic function can be broken down, into smaller sub-parts by using recursion.

**Program for factorial calculation:**

def recursive_factorial(n): if n == 1: return n else: return n*recursive_factorial(n-1) num = int(input("User Input :")) print("The factorial of", num, "is", recursive_factorial(num)) Output User Input :5 The factorial of 5 is 120

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