# Python working with functions

A function in python defined as a a group of statements that required to perform a task which takes required inputs and returns the output. We have two types of functions 1. built-in functions and 2. user defined functions. We have many built-in functions in python. You can see the list of pyhon built-in functions in in python documentation.

## Syntax of python function:

def function_name(arg1, arg2): # statement 1 # statement 2 return None

"def" is a keyword in python which is used to define the function in python. A python function may take or may not take arguments. In above syntax we have used return statement. The "return" statement is used to return the result of a function. If return statement is not included in the function code then the python function returns the "None" value by default.

## Python funciton to find the factorial of a number

def factorial(number): result = 1 for i in range(1, number+1): result = result * i return result # call the function print(factorial(4)) # Output: 24 print(factorial(5)) # Output: 120

Above function take a number and returns the factorial of that number. In above we have called the function twice. Each time we call the function we used difference input.