To find the Python factorial of a number, the number is multiplied with all the integers that lie between 1 and the number itself. Mathematically, it is represented by “!”. Thus, for example, 5! will be 5 x 4 x 3 x 2 x 1, that is 120. Factorial for negative numbers is not defined. Also, the factorial for number 0, that is, 0! is 1. Factorial of a number is frequently used in data analysis and higher mathematics problems.

## Factorial Program in Python

**Write a Python program to calculate the factorial of a number input by the user using the factorial () function.**

import math n = int (input (“Enter the number whose factorial you want to find: ”)) print (“The factorial of the number is: “) print (math.factorial (n))

**Write a program to calculate the factorial of a number in Python using FOR loop.**

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

If there is the possibility that the number entered can be zero as well, then the code will be as follows.

n = int (input (“Enter the number for which the factorial needs to be calculated: “) factorial = 1 if n < 0: print (“Factorial cannot be calculated, non-integer input”) elif n == 0: print (“Factorial of the number is 1”) else: for i in range (1, n+1): factorial = factorial *i print (“Factorial of the given number is: “, factorial)

**Write the Python program to calculate the factorial of a number using recursion.**

n = int (input (“Enter the number for which the factorial needs to be calculated: “) def rec_fact (n): if n == 1: return n elif n < 1: return (“Wrong input”) else: return n*rec_fact (n-1) print (rec_fact (n))

## FAQs on Python Factorial

*Q1. How do you calculate factorials in Python?*

**Python factorial** can be calculated in various ways. The three possible ways through which a Python code can calculate the factorial of a positive integer are provided below.

For Loop

Recursion

math.factorial()

*Q2.Does Python have a factorial?*

Yes, we can calculate the factorial of a number with the inbuilt function in Python. The function factorial () is available in the Python library and can be used to compute the factorial without writing the complete code.

The factorial () function is defined in the math module of Python. The internal implementation of the function is C type, thus the computation is fast.

**Syntax of factorial ():**

math.factorial (x)

Parameters Required: x represents the parameter required to be passed in the function. It is the number for which the factorial needs to be calculated.

Return value: The function will return the factorial of the number passed in the parameter. If the number is non-integer or a negative integer, then it will return an error value.

*Q3. How do you make a factorial loop in Python?*

In Python, if one wishes to write the complete code to calculate the factorial, then they can use the loop. While using a loop, there can be two cases.

When it is assured that the number input for which the **Python factorial** needs to be calculated is going to be positive, then one can simply use the FOR loop.

However, if the number input can be negative, non-integer, or zero, then if…else conditions will also be added to the code.

*Q4. How do you calculate factorials?*

**Python factorial** can also be calculated using recursion. Recursion is the process when a defined function can call itself. Thus, with recursion, one can loop through the data till the required answer is reached.

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