What is a Function?

Functions allow you to reuse code

• Performs a specific task
• Begins with the keyword def followed by the function name and parentheses ( )
• Any parameters or arguments will be placed in the parentheses ( )
• Docstrings (optional statements) which describes what the function does
• The return keyword exits a function

The Structure of a Function

• Keyword def is the function definition
• say_hi is the function name
• everything inside the function is the code block
• "Print 'Aloha!' greeting" is the docstring
• print('Aloha!') is the output
• say_hi( ) is calling (invoking) the function (executing the function, the code block)

Parameters or Arguments

Information that the function needs

• A parameter is a piece of information (a placeholder) that the function needs 
• An argument is a piece of information that is passed from a function call to a function

Return Values

The value that the function returns

Scope

Access to your variables based on location

• Global variables can be accessed throughout your entire program
• Local variables can be used only inside the function in which they are declared

practice!