# 第5章 面向对象编程（OOP）

## 5.1 面向对象概述

- **类（Class）**：抽象模板，定义属性和方法
- **对象（Object）**：类的实例
- **封装**：隐藏内部实现细节
- **继承**：子类继承父类的属性和方法
- **多态**：同一接口，不同实现

---

## 5.2 类和对象

```python
class Dog:
    species = "犬科"

    def __init__(self, name, age):
        self.name = name
        self.age = age

    def bark(self):
        return f"{self.name} 汪汪叫！"

    def __str__(self):
        return f"{self.name}（{self.age}岁）"

my_dog = Dog("旺财", 3)
print(my_dog.bark())
print(my_dog)
```

---

## 5.3 封装

```python
class BankAccount:
    def __init__(self, owner, balance=0):
        self.owner = owner
        self.__balance = balance

    def deposit(self, amount):
        if amount > 0:
            self.__balance += amount

    def get_balance(self):
        return self.__balance
```

---

## 5.4 继承

```python
class Animal:
    def __init__(self, name):
        self.name = name

class Cat(Animal):
    def speak(self):
        return f"{self.name} 喵喵叫"

class Dog(Animal):
    def speak(self):
        return f"{self.name} 汪汪叫"
```

---

## 5.5 魔术方法

```python
class Book:
    def __init__(self, title, author, price):
        self.title = title
        self.author = author
        self.price = price

    def __str__(self):
        return f"《{self.title}》 - {self.author}"

    def __repr__(self):
        return f"Book('{self.title}', '{self.author}', {self.price})"

    def __eq__(self, other):
        if isinstance(other, Book):
            return self.title == other.title
        return False
```

---

## 本章练习

1. 设计一个 `Student` 类，包含姓名、年龄、成绩属性
2. 使用继承创建 `Animal` 类及其子类
3. 实现一个单例模式的配置管理器类