Methods, and when objects beat dicts

Behavior lives in methods

A method is a function defined inside a class. It always takes self first, which is how it reaches the object's own attributes. You have been calling methods all along: "hi".upper() and my_list.append(3) from Python for Beginners are methods on str and list objects.

class Player:
    def __init__(self, name):
        self.name = name
        self.score = 0

    def add_points(self, points):
        self.score += points

When you write mia.add_points(10), Python translates it to Player.add_points(mia, 10). That is the whole mystery of self: it is the object before the dot.

Dict or class?

Both model "a thing with named parts". Use this rule:

A class gives you three wins over the dict version:

• Typo safety: mia.scor raises AttributeError immediately, while player["scor"] silently creates a new key on assignment.
• A home for logic: add_points lives next to the data it changes.
• A contract: every Player is guaranteed to have name and score, because __init__ sets them.

In unit 8 you will parse JSON, a text format for structured data defined there, into dicts, then convert the important pieces to objects at the boundary. That combination is everyday production Python.