How do you find the factorial of a number in Python?

Calculating the factorial of a number is a common operation in programming, and there are several ways to achieve it in Python. The factorial of a number is the product of all positive integers less than or equal to that number. For example, the factorial of 5 is 5! = 5 * 4 * 3 * 2 * 1 = 120.

In this article, we will explore different methods for calculating the factorial of a number in Python, including using a while loop, a for loop, recursion, and a class. These methods provide different approaches to solving the problem and offer varying levels of complexity.

How to find the factorial of a number in Python using while loop?

To find the factorial of a number in Python using a while loop, we can use the following code:

def factorial_while(n):
    result = 1
    while n > 1:
        result *= n
        n -= 1
    return result

print(factorial_while(5))  # Output: 120Copy

In the above example, the factorial_while() function takes an integer n as an argument and returns the factorial of n using a while loop. It initializes a variable result to 1 and then enters the loop, which runs as long as n is greater than 1. Inside the loop, it multiplies result by n and decrements n by 1. When the loop exits, it returns the value of result.

Factorial of a number in Python using for loop

To find the factorial of a number in Python using a for loop, we can use the following code:

def factorial_for(n):
    result = 1
    for i in range(2, n+1):
        result *= i
    return result

print(factorial_for(5))  # Output: 120Copy

Python program to find factorial of a number using recursion

def factorial_recursion(n):
    if n == 1:
        return 1
    else:
        return n * factorial_recursion(n-1)

print(factorial_recursion(5))  # Output: 120Copy

In the above Python program to find factorial of a number using recursion example, the factorial_recursion() function takes an integer n as an argument and returns the factorial of n using recursion. It checks if n is equal to 1 and, if so, returns 1. If n is not equal to 1, it returns n multiplied by the factorial of n-1, which is calculated recursively.

Factorial program in Python using Class

Here’s an example of a class in Python that can calculate the factorial of a number:

# Calculate the factorial of a number using a class in Python

class Factorial:
  # Initialize the class with the number attribute
  def __init__(self, number):
    self.number = number

  # Define the calculate method to compute the factorial
  def calculate(self):
    # Iterate from 1 to the number and multiply the factorial by each number
    factorial = 1
    for i in range(1, self.number+1):
      factorial *= i
    return factorial

# Create an instance of the Factorial class with the number 5
factorial = Factorial(5)
# Call the calculate method on the instance and print the result
print(factorial.calculate())  # Output: 120Copy

Above example code for Factorial program in Python using Class defines a Factorial class with a __init__ method to initialize the class with a number attribute, and a calculate method to compute the factorial of that number. It then creates an instance of the Factorial class with the number 5 and calls the calculate method on it to print the result. The output will be 120, which is the factorial of 5.

How to find factorial of a number in Python without using function?

You can find the factorial of a number in Python without using a function by using a loop and keeping track of the result in a variable. Here’s an example of How to find factorial of a number in Python without using function :

# Initialize the result variable to 1
result = 1

# Get the number for which to calculate the factorial
number = 5

# Iterate from 1 to the number and multiply the result by each number
for i in range(1, number+1):
  result *= i

# Print the result
print(result)Copy

This will output 120, which is the factorial of 5.