Python Program to Find the Factorial of an Integer

In this article, we will find the factorial of a number with python.

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The factorial of a number is the product of all the integers from 1 to that number.

For example, the factorial of 6 is 1*2*3*4*5*6* = 720.

Factorial is not defined for negative numbers, and the factorial of zero is one, 0! = 1.

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We will implement two methods to solve the factorial of a number.

Method 1:

Step 1:

First, we will define the factorial function which will take an interger argument n.

def factorial(n):

Step 2:

Initialising the factorial to 1

factorial = 1

Step 3:

If n is equal to 0 the factorial will be 1 by default.

if n == 0: return 1

Step 4:

Else, we implement a for loop to iterate through intergers ranging from 1 to n to return their product.

else:
    for i in range(1,n+1):
        factorial *= i
return factorial

Let's apply this code !

factorial(8)
40320

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Method 2:

Step 1: Recursive function

We will implement a function that recursively calls itself by decreasing the number..

First, we will define the factorial_rec function which will take an interger argument n.

def factorial_rec(n):

Step 2:

Base condition n=0 :

if n == 0:
    return 1

Step 3:

Recursion:

return factorial_rec(n-1)

Let's apply this code !

factorial_rec(5)
120
factorial_rec(0)
1

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source code