# How To Do Factorial In Python?

Python has a built-in function called factorial() that calculates the factorial of a number. But what if you want to calculate the factorial of a number without using this function?

In this blog post, we’ll show you how to do factorial in Python without using the factorial() function. We’ll also discuss some of the benefits of doing this.

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## Introduction

In mathematics, the factorial of a positive integer n, denoted by n!, is the product of all positive integers less than or equal to n:

n! = 1 × 2 × 3 × ⋯ × n

For example, 5! = 5 × 4 × 3 × 2 × 1 = 120.

The value of 0! is 1, according to the convention for an empty product.

## What is a factorial?

A factorial is a function that multiplies a number by every number below it. For example, 5! (said “5 factorial”) is 5 * 4 * 3 * 2 * 1.

Factorials are used often in mathematics, especially in combinatorics, where they give the number of ways to arrange objects.

## How to do factorial in Python?

To calculate the factorial of a number in Python, you can use the math.factorial() method. This method takes an integer as an argument and returns the factorial of that number.

For example, if you want to calculate the factorial of 5, you would do the following:

>>> import math
>>> math.factorial(5)
120
As you can see, the factorial of 5 is 120.

## Using the math module

Factorial is a mathematical operation which returns the product of all positive integers less than or equal to a given number.

The factorial of 4 (denoted as 4!) is 1×2×3×4=24.

As you can see, the factorial operation is not defined for negative numbers and zero. In Python, you can calculate the factorial of a number using the math module.

To do this, you first need to import the math module using the following code:

import math

You can then use the math.factorial() function to calculate the factorial of a number. For example, to calculate the factorial of 4, you would use the following code:

math.factorial(4)
#Output: 24

## Using the factorial function

The factorial function is a mathematical function that calculates the product of all positive integers less than or equal to a given number. The factorial of a number is typically denoted by the symbol “!” and is often referred to as the “factorial” of that number. For example, the factorial of 5 is 5! = 5 x 4 x 3 x 2 x 1 = 120.

There are a few different ways to calculate the factorial of a number in Python. One way is to use the built-in math module:

import math
math.factorial(5) # Returns 120

Another way is to use a for loop:

## Using recursion

In mathematics, the factorial of a positive integer n, denoted by n!, is the product of all positive integers less than or equal to n. For example,

5! = 5 * 4 * 3 * 2 * 1 = 120.
The value of 0! is 1, according to the convention for an empty product.

## What are the benefits of using recursion?

There are a number of benefits to using recursion when doing factorial in Python, chief among them being that it is easy to understand and code. Additionally, when the input number is large, recursion can be faster than looping since it avoids having to store all the interim values in memory. Finally, recursion can occasionally lead to more efficient code since it avoids having to perform certain operations (such as multiplication) more than once.

## What are the drawbacks of using recursion?

There are many Factorial algorithms in existence, but the na\”ive algorithm is both conceptually simple and easy to program. However, there are some drawbacks to using recursion which include:
-It can be computationally expensive as it requires additional memory to store the function call stack.
-There is a risk of a stack overflow if the recursion goes too deep.
-It can be difficult to debug as it is not always easy to follow the flow of execution.

For these reasons, it is often preferable to use an iterative algorithm for calculating the factorial of a number.

## Conclusion

To find the factorial of a number in Python, you can use the factorial() function from the math module. This function takes an integer as an argument and returns the factorial of that number. The factorial of a number is the product of all the integers from 1 to that number. For example, the factorial of 5 is 1 x 2 x 3 x 4 x 5 = 120.

You can also find thefactorial of a number using a for loop. To do this, you would first initialize a variable to 1 and then use a for loop to multiply that variable by every integer from 1 to the number you want to find the factorial of. For example, if you wanted to find the factorial of 5 using a for loop, your code would look like this:

“`
result = 1
for i in range(1, 6):
result = result * i
print(“The factorial of 5 is”, result)
“`

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