Functions

Functions

Review lesson. A summary of the functions part of Module 1, for quick reference and self-checking after unit 1.9.

Syntax and parameters

def area(width, height=1, *extras, **options):
    return width * height

Concept	Meaning
Parameter	A name in the function definition (width, height)
Argument	A value passed at call time (area(3, 4))
Default parameter	height=1 — used when no argument is passed
*args	Collects extra positional arguments into a tuple
**kwargs	Collects keyword arguments into a dict
return a, b	Returns multiple values (actually a tuple)
lambda x: x ** 2	A one-line anonymous function, often used as key= for sorted

Variable scope

• Assigning inside a function creates a new local variable and does not change a variable with the same name outside.
• To change an outer variable, you must declare global x inside the function (use sparingly; prefer passing values in and using return).

Remember

• A function should do one thing and have a name that says what it does.
• Place parameters that have default values after the required parameters.