# Calculates the factorial of a given number in Python

#### Calculates the factorial of a given number in Python

Write a Python Program to Factorial of a given Number Factorial in Mathematics:

In mathematics, the factorial of a non-negative integer ‘n’ is the product of all positive integers less than or equal to ‘n’  It is denoted by n! Mathematically,

n!=n×(n-1)×(n-2)×…×3×2×1

For example,5!=5×4×3×2×1=120

5!=5×4×3×2×1=120.

Python Program to Calculate Factorial:

Here’s a Python program that calculates the factorial of a given number:

 num = int(input("Enter a number: ")) factorial = 1 if num < 0:     print("Factorial is not defined for negative numbers.") elif num == 0:     print("Factorial of 0 is 1.") else:     for i in range(1, num + 1):         factorial *= i     print("Factorial of", num, "is", factorial)

Explanation:

1. The program starts by taking an integer input from the user using the input() function and converting it into an integer using the int() function. This input is stored in the variable num.
2. The variable factorial is initialized to 1. This will store the result of the factorial calculation.
3. The program uses conditional statements (if, elif, and else) to handle different cases:
• If the input is negative, it prints that factorial is not defined for negative numbers.
• If the input is 0, it prints that the factorial of 0 is 1.
• Otherwise, it calculates the factorial using a for loop that iterates from 1 to num + 1, and at each step, updates the factorial by multiplying it with the current value of i.
1. After the loop, the program prints the calculated factorial.

Output:

Enter a number: 5 Factorial of 5 is 120

In this example, if the user enters the number 5, the program calculates the factorial of 5 using the formula \( 5! = 5 \times 4 \times 3 \times 2 \times 1 = 120 ) and displays “Factorial of 5 is 120” as the output.