AtomicReference 困难和替代方案(AtomicReference difficulties and alternatives)

 你定义的value不是你的类的实例字段，它更像是一个静态字段。 但是python不介意你是否从实例中访问这个字段。 因此，即使您从实例访问此字段，它也不是每个实例的不同列表。 基本上，每次调用该方法时都会追加到相同的列表中。 
 
 你必须这样做 
 
class A(object):

    def __init__(self):
        self.value = []

    def method(self, new_value):
        self.value.append(new_value)
 
 现在您为每个实例创建了不同的列表。 
 
 编辑 ：让我试着解释当你使用str时会发生什么。 
 
class A(object):

    self.value = 'str'

    def method(self):
        self.value += '1'
 
 前面代码中的最后一行与此相同： 
 
        self.value = self.value + '1'
 
 现在，这使得它更容易看到发生了什么。 首先，python从self.value获取值。 既然没有自定义的实例字段，这会给'str' 。 将'1'添加到该字段并将其设置为名为value的实例字段。 这就像 
 
self.value = 'str1'
 
 这与您在__init__方法中设置实例字段（在我的第一个代码片段中）是一样的。 
 
self.value = []
 
 这是否清楚？ 

The value you are defining is not an instance field for your class, its more like a static field. But python doesn't mind if you access this field from instances. So, even if you access this field from instances, it is not a different list for each instance. Basically, you are appending to the same list every time the method is called.
 
You'll have to do this
 
class A(object):

    def __init__(self):
        self.value = []

    def method(self, new_value):
        self.value.append(new_value)
 
Now you have a different list created for each instance.
 
EDIT: Let me try to explain what happens when you use a str.
 
class A(object):

    self.value = 'str'

    def method(self):
        self.value += '1'
 
That last line in the previous code is the same as this:
 
        self.value = self.value + '1'
 
Now, this makes it abit easier to see what's going on. First, python gets the value from self.value. Since there is no instance field defined yet on self, this will give 'str'. Add '1' to that and sets it to the instance field called value. This is like
 
self.value = 'str1'
 
which is the same as you'd set an instance field in the __init__ method (in my first snippet of code).
 
self.value = []
 
Does that make it clear?