Python Program to Find Factorial of a Number

Python programs to find factorial of number example; In this tutorial, you will learn how to find factorial of given number or user-inputted number in python using while loop, for loop and recursion fuction.

Factorial, in mathematics, the product of all positive integers less than or equal to a given positive integer and denoted by that integer and an exclamation point. Thus, factorial seven is written 7!, meaning 1 × 2 × 3 × 4 × 5 × 6 × 7. Factorial zero is defined as equal to 1.

Find the Factorial of a Number in Python

Let’s use the following algorithm to write a program to calculate/find the factorial of a number in python:

• Python Program find factorial using using While Loop
• Factorial of a number in python using for loop
• Factorial of a number in python using recursion

Python Program find factorial using using While Loop

Follow the below steps and write a python program to find factorial of a number using while loop

• Take input from the user
• Define fact variable
• Iterate while loop and find factorial of given number and store it
• Print factorial

num = int(input("enter a number: "))
 
fact = 1
i = 1
 
while i <= num:
 fact = fact * i
 i = i + 1
 
print ("Factorial of the number %d is %d" %(num, fact))

Output

enter a number: 5
Factorial of the number 5 is 120

Factorial of a number in python using for loop

Follow the below steps and write a python program to find factorial of a number using for loop

• Take input from the user
• Define fact variable
• Iterate for loop and calculate factorial of number
• Print the final result

#Python program to print factorial of a number
num = int(input("Enter the number: "))
fact = 1

#iterating through the num value
for i in range (1, num+1):
    fact = fact*i

#printing the output
print ("Factorial of the number %d is %d" %(num, fact))

Output

Enter the number: 10
Factorial of the number 10 is 3628800

Factorial of a number in python using recursion

Follow the below steps and write a python program to find factorial of a number using recursion

• Define a function to calculate factorial of given number
• Take input from the user
• Use if else statement to check input number
• Call above define factorial function
• Print the final result

# Factorial of a number using recursion

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

num = int(input("Enter the number: "))

# check if the number is negative
if num < 0:
   print("Sorry, factorial does not exist for negative numbers")
elif num == 0:
   print("The factorial of 0 is 1")
else:
   print("The factorial of", num, "is", recur_factorial(num))

Output

Enter the number: 6
The factorial of 6 is 720

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