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解析 Python 类里类变量的修改方式

news 2026/6/23 0:41:40

在 Python 类中，类变量是属于类本身的变量，所有实例共享同一内存空间。修改类变量的方式主要有两种：通过类名修改和通过实例修改，但两者的效果截然不同，需要重点区分。

1. 通过类名修改类变量（推荐）

通过类名直接修改类变量，会真正改变类变量的值，所有实例访问该变量时都会获取到更新后的值。

示例：

python

运行

class MyClass: class_var = "初始值" # 类变量 # 通过类名修改类变量 MyClass.class_var = "修改后的值" # 所有实例访问的都是修改后的值 obj1 = MyClass() obj2 = MyClass() print(obj1.class_var) # 输出：修改后的值 print(obj2.class_var) # 输出：修改后的值 print(MyClass.class_var) # 输出：修改后的值

2. 通过实例修改类变量（不推荐，易混淆）

通过实例修改类变量时，不会改变类本身的变量，而是会给该实例创建一个同名的实例变量，此后该实例访问该变量时，会优先使用自己的实例变量（屏蔽类变量），而其他实例和类本身访问的仍然是原来的类变量。

示例：

python

运行

class MyClass: class_var = "初始值" # 类变量 obj1 = MyClass() obj2 = MyClass() # 通过实例 obj1 "修改" 类变量（实际是创建实例变量） obj1.class_var = "obj1的实例变量" # 实例 obj1 访问的是自己的实例变量 print(obj1.class_var) # 输出：obj1的实例变量 # 实例 obj2 和类本身访问的仍是原来的类变量 print(obj2.class_var) # 输出：初始值 print(MyClass.class_var) # 输出：初始值

总结

通过类名修改：会全局更新类变量，影响所有实例。
通过实例修改：不会改变类变量，只会给该实例新增一个同名实例变量，仅影响当前实例。

实际开发中，建议始终通过类名修改类变量，避免通过实例修改导致的逻辑混淆。

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