Python--面向对象进阶（下）

4. 特殊成员 方法作用示例​__init__​初始化对象​obj = MyClass()​​__new__​创建对象（构造方法）返回对象实例​__call__​使对象可调用​obj()​​__str__​定义对象的字符串表示​print(obj)​​__getitem__​实现索引访问​obj[key]​​__enter__/__exit__​上下文管理（with语句）​with obj as ctx: ...​

示例：上下文管理

class Database: def __enter__(self): print("连接数据库") return self def __exit__(self, *args): print("关闭连接") with Database() as db: print("执行查询操作") # 输出： # 连接数据库 # 执行查询操作 # 关闭连接

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5. 迭代器与生成器 5.1 迭代器 实现__iter__​和__next__​ class Counter: def __init__(self, max_num): self.current = 0 self.max = max_num def __iter__(self): return self def __next__(self): if self.current < self.max: self.current += 1 return self.current raise StopIteration for num in Counter(3): print(num) # 输出1, 2, 3 5.2 生成器 使用yield​简化迭代器 def counter(max_num): current = 0 while current < max_num: current += 1 yield current for num in counter(3): print(num) # 输出1, 2, 3 5.3 可迭代对象 仅需实现__iter__​并返回迭代器 class MyRange: def __init__(self, max_num): self.max = max_num def __iter__(self): return iter(range(self.max)) for num in MyRange(3): print(num) # 输出0, 1, 2