EASY WAY TO CALCULATE FACTORAIL OF NUMBER IN PYTHON

Introduction:

In this program, we will calculate the factorial of a given number. A factorial of a non-negative integer nnn, denoted as n!n!n!, is the product of all positive integers less than or equal to nnn. Factorials are used in various fields like mathematics, statistics, and computer science.

Python Program to Calculate Factorial:

# Introduction to the program:
# This program calculates the factorial of a given number entered by the user.

# Function to calculate factorial of a number using recursion
def factorial(n):
    # Base condition: factorial of 0 or 1 is 1
    if n == 0 or n == 1:
        return 1
    else:
        # Recursive case: n * factorial(n-1)
        return n * factorial(n - 1)

# Input: Asking the user to enter a non-negative integer
n = int(input("Enter a non-negative integer: "))

# Output: Checking if the number is non-negative and calculating the factorial
if n < 0:
    print("Factorial is not defined for negative numbers.")
else:
    print(f"The factorial of {n} is: {factorial(n)}")

Explanation of the Syntax:

Function Definition:

def factorial(n):

def is used to define a function named factorial.

n is the argument passed to the function, which represents the number for which the factorial will be calculated.

Base Condition:

if n == 0 or n == 1:
    return 1

The base condition checks if the input is 0 or 1. The factorial of 0 and 1 is 1, so the function returns 1.

Recursive Case:

else:
    return n * factorial(n - 1)

If n is greater than 1, the function calls itself recursively with n - 1. The product of n and factorial(n - 1) gives the factorial of n.

User Input:

n = int(input("Enter a non-negative integer: "))

input() prompts the user to enter a number.

int() converts the input into an integer, since input() returns a string by default.

Condition to Check Negative Input:

if n < 0:
    print("Factorial is not defined for negative numbers.")

This if statement ensures that the user doesn’t enter a negative number. If they do, a message is displayed saying that factorials are not defined for negative numbers.

6.Printing the Result:

print(f"The factorial of {n} is: {factorial(n)}")

The print() function displays the result.f"The factorial of {n} is: {factorial(n)}" is an f-string used to format the output, where {n} is the number entered by the user, and {factorial(n)} is the result of the function.

Sample Output:

Enter a non-negative integer: 5
The factorial of 5 is: 120

Conclusion:

In this program, we explored how to calculate the factorial of a number using recursion. The program ensures that the user enters a non-negative integer and handles negative inputs by displaying an appropriate message. We used recursion to simplify the process of calculating the factorial, which is a great example of breaking down a complex problem into smaller sub-problems.

This program introduces fundamental concepts of recursion, function definitions, and conditional statements in Python.

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