# Function in Python

Introduction to function

What is function
-Function consists of a group of statements
-Its main function is to perform one intended job. For example creating a function to calculate area of a circle

Examples of built-in function in Python
-print() : Use to display output on screen
-input() : Taking input from user
-sqrt() : To calculate square root

Can we create user defined function
-Yes

What is user defined function
-Function which are created by programmers

-Same function can be called multiple times which causes to reduce length of a program

-Function can be easily added, deleted or modified

-Debugging becomes easy

How to define or create a function
-To create a function use keyword def followed by function name.
-After function name, write parenthesis() which may or may not contain parameters
-Include colon after parenthesis

Syntax

def function_name(parameter1, parameter2):

Example : Create a function to calculate sum of two values

```def sum(a,b):
result = a+b
print(result)```

In above lines, sum is the name of the function. a and b are parameters. Parameters receives data from outside or when the function is called

How function can be called or executed
-Use function name to call it
-In order to call sum(), use it function name such as sum()
-Passed necessary values inside parenthesis
sum(10,4)

```def sum(a,b):
print('Value of a parameter:',a)
print('Value of b parameter:',b)
result = a+b
print(result)```

sum(10,4) #Function is called. Passing two values to a and b parameters. Value 10 and 4 will be passed onto parameter a and b respectively.

Output

```Value of a parameter: 10
Value of b parameter: 4
Sum of 10 and 4 is 14```