Set 3 - Functions

function

A reusable block of code that performs a specific task.

def function_name(parameters):

How to define a function.

return

The keyword used to exit a function and send a value back.

parameter

A variable listed inside parentheses in a function definition.

argument

The actual value passed into a function when it's called.

return None

Indicates the function has no explicit return value.

scope of a variable

Local — it exists only inside that function.

mutable arguments

Changes inside the function affect the original object.

immutable arguments

They do not change the original variable.

function call vs definition

A definition creates it; a call executes it.

function call

function_name(arguments)

return multiple values

Return them as a tuple → return a, b, c

capture multiple return values

x, y, z = function()

docstring

To describe what a function does (written as """Description""").

two functions with the same name

The later one overwrites the earlier.

modify a global variable

Only if declared with global var_name.

better practice than modifying globals

Pass values in and return results instead.

top-down design

Breaking a program into smaller, manageable functions.

why use functions

Reusability, readability, debugging simplicity.

printing vs returning

Printing displays output; returning makes data reusable.

default values for parameters

def func(x, y = 10):

call a function without required arguments

It raises a TypeError.

pass expressions as arguments

Yes — they're evaluated before the call.

comment inside functions

Use # for single-line comments.

placeholder function

pass

returning early from a function

Using return inside an if to exit early based on a condition.