In this post, you will learn a program to find the factorial of an N number using for-loop, recursion, while-loop, function, and so on but before writing a program you should know about the factorial number.

What is a Factorial number?

Factorial of N number is defined as the product of all the numbers greater or equal to 1 and it is denoted by (N ! ).

For Example: 5! = 5*4*3*2*1 = 120

Formula and Example for Factorial of N numbers

Now let’s write a Python program to find the factorial of N number by using different approaches.

Python program to find Factorial of N number using while loop.

Before writing a program you should know about:

  1. while loop
  2. Arithmetic Operators

Source code

num = int(input('Enter a number: '))
factorial = 1

i = 1
while i <= num:
    factorial *= i
    i = i + 1

print(f"Factorial of {num} is {factorial}")

Output

Enter a number: 7
Factorial of 7 is 5040

Program to find Factorial of N number in python using for loop.

Before writing a program you should about:

  1. for loop
  2. Arithmetic Operators

Source code

my_num = int(input('Enter a number: '))

facto = 1
for i in range(1,my_num+1):
    facto *= i

print(f"Factorial of {my_num} is {facto}")

Output

Enter a number: 5
Factorial of 5 is 120

Python program to find Factorial of N number using function.

Few things you should know before writing this program:

  1. for loop
  2. Python function
  3. Arithmetic Operators

Source code

def facto(n):
    f = 1
    for i in range(1,n+1):
        f *= i
    return f

num = int(input('Enter a number: '))

my_facto = facto(num)

print(f"factorial of {num} = {my_facto}")

Output

Enter a number: 4
factorial of 4 = 24

We should also write above program using built-in function.

Python program to find Factorial of N number using the built-in function.

there is one built-in function inside the math module called factorial() and using this function we can get easily factorial of any number

Source code

from math import factorial

# print(factorial(5))
# print(factorial(7))
# print(factorial(6))

# ********* OR *********

my_num = int(input('Enter a number: '))
print(f'factorial of {my_num} = {factorial(my_num)}')

Output

Enter a number: 3
factorial of 3 = 6

Factorial of N number in python using recursion

def N_factorial(num):
    if num <= 1:
        return 1
    else:
        return num * N_factorial(num - 1)

number = int(input('Enter your number: '))
fac = N_factorial(number)

print(f'factorial of {number} = {fac}')

Output:

Enter your number: 8
factorial of 8 = 40320
Author

Hi, I'm Yagyavendra Tiwari, a computer engineer with a strong passion for programming. I'm excited to share my programming knowledge with everyone here and help educate others in this field.

1 Comment

  1. Rusimbi William Reply

    Thank you for, can you do some algorithms of finding the Fibonacci sequence

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