如何避免在实例之间共享类数据? [英] How to avoid having class data shared among instances?

问题描述

我想要的是这种行为:

class a:
    list = []

x = a()
y = a()

x.list.append(1)
y.list.append(2)
x.list.append(3)
y.list.append(4)

print(x.list) # prints [1, 3]
print(y.list) # prints [2, 4]

当然，当我打印时真正发生的是:

Of course, what really happens when I print is:

print(x.list) # prints [1, 2, 3, 4]
print(y.list) # prints [1, 2, 3, 4]

显然他们正在a 类中共享数据.我如何获得单独的实例来实现我想要的行为?

Clearly they are sharing the data in class a. How do I get separate instances to achieve the behavior I desire?

推荐答案

你想要这个:

class a:
    def __init__(self):
        self.list = []

在类声明中声明变量使它们成为类"成员而不是实例成员.在 __init__ 方法中声明它们可确保在对象的每个新实例旁边创建成员的新实例，这是您正在寻找的行为.

Declaring the variables inside the class declaration makes them "class" members and not instance members. Declaring them inside the __init__ method makes sure that a new instance of the members is created alongside every new instance of the object, which is the behavior you're looking for.

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