Here are three ways to find the factorial of a number in Python.
- Using “for loop”
- Using “recursion”
- Using “math.factorial()” method
Method 1: Using for loop
You can use a “for loop” to iterate through number 1 till the designated number and keep multiplying at each step.
num = input("Enter a number: ")
factorial = 1
if int(num) >= 1:
for i in range(1, int(num)+1):
factorial = factorial * i
print("Factorial of ", num, " is : ", factorial)Output
Enter a number: 4
Factorial of 4 is : 24
Method 2: Using recursion
A recursive function is a function that calls itself during its execution. This enables the function to be repeated several times, as it can call itself during its execution.
def factorial(n):
if n == 0:
return 1
else:
return n * factorial(n-1)
print(factorial(4))Output
Factorial of 4 is: 24
Method 3: Using math.factorial() method
To calculate the factorial of a number in Python, you can use the built-in “math.factorial()” method.
Syntax
math.factorial(num)
Parameters
num: It is an integer. If we provide float or any negative number, it will throw an error.
Return Value
The “factorial()” method returns the factorial of the desired number.
Example 1
# Taking input from user
num = int(input("Enter the number to find factorial: "))
# Declaring one temporary variable to store the answer
fact = 1
# Finding factorial of the given number
for i in range(1, num+1):
fact = fact*i
print("Factorial of the given number ", num, " is: ", fact)
Output
Enter the number to find factorial: 5
Factorial of the given number 5 is: 120Example 2: If the given number is Negative
import math
num = input("Enter a number: ")
print("The factorial of ", num, " is : ")
print(math.factorial(int(num)))Output
That’s it.
Ankit Lathiya is a Master of Computer Application by education and Android and Laravel Developer by profession and one of the authors of this blog. He is also expert in JavaScript and Python development.
