Classes and Instances

Scenario: A monitoring program passes several related service values through every function.

New words, in plain English

• Class - a blueprint defining data and behavior
• Instance - one object created from a class
• Attribute - data stored on an object
• Method - a function defined on a class

Classes group state and behavior when those belong together. Creating an instance calls the class. self is the current instance and is passed automatically to instance methods.

Analogy: A Python program is like a clear set of instructions for a careful helper: names label things, indentation groups steps, and errors explain where the helper became confused.

A small, real example

class Service:
    def healthy(self):
        return self.status == "up"

api = Service()
api.status = "up"
print(api.healthy())

Tip: Use a class when behavior protects or explains related state, not merely to wrap one dict.

Goal: Practice this idea in the py-small-class challenge at /labs/python. Fix the broken program, run it yourself, then use check to prove the real end state.