Defining Functions

In this chapter we cover how to define custom functions.

Functions are defined using the keyword def.

The basic syntax for creating a function is:

def function_name(arguments):
    Code block
    return return_value

where

• everything indented after the : is part of the function body

• arguments can be multiple arguments with names to refer to in the function body

• the return statement exits the function and returns the return_value

The function above can be called in the usual way: function_name(argument_values)

Worked Example

As a first example, let’s create a function that takes a single argument and doubles it’s value

def double(value):
    return 2*value

Again, we can call this argument by name and enter a value or variable as an argument:

double(1)

2

double(5.5)

11.0

double('a')

'aa'