Master Python OOP: From Classes to Real‑World Objects

Object‑Oriented Basics

Python was designed as an object‑oriented language. The core ideas of OOP are often summarized as encapsulation, inheritance, and polymorphism, although the concept itself is more abstract.

What Is Object‑Oriented Programming?

Object‑Oriented Programming (OOP) abstracts a real‑world entity into its attributes and behaviors, then analyzes, designs, and implements a complete program based on that abstraction.

OOP Process Flow

Object‑Oriented Analysis (OOA)

Object‑Oriented Design (OOD)

Object‑Oriented Programming (OOP)

Object‑Oriented Testing (OOT)

Object‑Oriented Maintenance (OOSM)

Defining a Class in Python

A class is a custom data type whose attributes can be of any type.

class <ClassName>(BaseClasses):
    class variables...
    def __init__(self, ...):
        # initializer
    def method(self):
        # instance method
    @staticmethod
    def static_method():
        pass
    @classmethod
    def class_method(cls):
        pass
    def __del__(self):
        # destructor

Example: collecting phone information.

class Phone:
    def __init__(self, name, screen_size, color, ram, rom, camera, battery, price, use):
        self.name = name
        self.screen_size = screen_size
        self.color = color
        self.ram = ram
        self.rom = rom
        self.camera = camera
        self.battery = battery
        self.price = price
        self.use = use
    def do(self):
        print('经常使用手机' + self.use)

xxx_phone = Phone('iphone11', '6.1英寸', '黑色', '3GB', '128GB', '1200万', '3200mAh', 5499, '打游戏')
print('品牌：{}, 屏幕大小：{}, 颜色：{}, 运行内存：{}, 机身存储：{}, 像素：{}, 电池容量：{}, 价格：{}'.format(
    xxx_phone.name, xxx_phone.screen_size, xxx_phone.color, xxx_phone.ram, xxx_phone.rom,
    xxx_phone.camera, xxx_phone.battery, xxx_phone.price))
xxx_phone.do()

Output:

品牌：iphone11,屏幕大小：6.1英寸,颜色：黑色,运行内存：3GB,机身存储：128GB,像素：1200万,电池容量：3200mAh,价格：5499
经常使用手机打游戏

Important Class Conventions

Class names should start with a capital letter.

Always define an __init__ method.

The first parameter of instance methods is conventionally named self.

Object Construction Process

The steps are: allocate memory with __new__, initialize with __init__, then return the object reference.

class Phone:
    def __new__(cls, *args, **kwargs):
        print('我先执行，开辟内存空间')
        return object.__new__(cls)
    def __init__(self, name):
        self.name = name
        print('实例化对象')
    def __del__(self):
        print('对象被销毁前执行我')

phone1 = Phone('iphone 11')
phone2 = Phone('iphone x')
print(phone1.name)
print(phone2.name)

Result shows the order of __new__ and __init__ calls and the destructor execution when objects are garbage‑collected.

Garbage Collection

Python uses a garbage collector that automatically calls an object's destructor before reclaiming memory. Common strategies include reference counting, mark‑and‑sweep, and generational collection.

Equality vs. Identity

Operator == compares values, while is compares object identities (memory addresses).

phone1 = Phone('iphone 11')
phone2 = Phone('iphone 11')
print(phone1.name == phone2.name)  # True
print(phone1 == phone2)            # False (different objects)
print(phone1 is phone2)            # False

To make two objects compare equal by ==, override __eq__:

class Phone:
    def __init__(self, name):
        self.name = name
    def __eq__(self, other):
        return self.name == other.name

phone1 = Phone('iphone 11')
phone2 = Phone('iphone 11')
print(phone1 == phone2)  # True

Class Attributes

Attributes defined directly in the class body are shared by all instances.

class Phone:
    owner = 'me'
    def __init__(self, name):
        self.name = name

phone1 = Phone('华为')
phone2 = Phone('荣耀')
print(Phone.owner)
print('这部' + phone1.name + '手机属于:' + phone1.owner)
print('这部' + phone2.name + '手机属于:' + phone2.owner)

OOP vs. Procedural Programming

Procedural programming follows a linear sequence of steps, while OOP first models the problem domain with classes and then creates many objects from those templates, making it suitable for larger, more complex projects.

Conclusion

The article introduced the philosophy of object‑oriented programming, basic class definitions, member and class attributes, and demonstrated how Python implements these concepts, providing a foundation for anyone learning Python.