Calculate a Number Factorial in Python

This python tutorial help to calculate factorial using Numpy and without Numpy. The factorial is always computed by multiplying all numbers from 1 to the number given. The factorial is always found for a positive integer.

in python, we can calculate a given number factorial using loop or math function, I’ll discuss both ways to calculate factorial for a number in python.

Using for Loop

We can use a for loop to iterate through number 1 until we get to the given number, multiplying each time.

n = input("Enter a number: ")
factorial = 1
if int(n) >= 1:
for i in range (1,int(n)+1):
factorial = factorial * i
print("Factorail of ",n , " is : ",factorial)

Output:

Enter a number: 4
Factorial of 4 is : 24

Calculate Factorial Using Recurssion

We can also calculate factorial using recursively way.

num = input("Enter a number: ")
def fact_recursive(n):
if n == 1:
return n
elif n < 1:
return ("NA")
else:
return n*fact_recursive(n-1)
print("The factorial of ", num, " is : ")
print (fact_recursive(int(num)))

Output:

Enter a number: 5
The factorial of 5 is :
120

Calculate Factorial Using math.factorial()

The factorial function in the math module can be used directly. We can utilize math.factorial instead of writing the code for factorial functionality. Negative and fractional numbers are likewise taken care of in this way.

import math
num = input("Enter a number: ")
print("The factorial of ", num, " is : ")
print(math.factorial(int(num)))

Output:

Enter a number: 5
The factorial of 5 is :
120

Factorial of an integer with NumPy in Python

We can also calculate a number factorial using NumPy library. The numpy.math.factorial() method is used to calculate the factorial of a number.

import numpy as np
num = input("Enter a number: ")
factorial = np.math.factorial(int(num))
print("Factorail of ",num , " is : ",factorial)

Output:

Enter a number:
6
Factorail of 6 is : 720