L3·Functions & Modules

🧩Defining Functions

def, return, default arguments, docstrings.

defreturndocstring

§ 1def

def name(params): body. Return with return; without it, returns None.

§ 2Default arguments

Evaluated once at definition. Never use mutable defaults like [] or {} — use None + assign inside.

§ 3Docstrings

First string in the body becomes .__doc__. Show up in help().

Animated step-through

step 1 / 6// Call greet('Ada')

1def greet(name, greeting="Hello"):
2    """Return a friendly greeting."""
3    return f"{greeting}, {name}!"
4
5print(greet("Ada"))
6print(greet("Bob", greeting="Hi"))

Variables

— none yet —

Call stack

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Checkpoint quiz

Question 1 / 2

What does 'return' with no value give?

Sets

*args & **kwargs