使用__处理全局变量的Python名称 [英] Python name mangling on global variable with __

问题描述

当我使用 __ 创建模块级变量并尝试在类的方法(使用 global 关键字)中访问它时，发生了名称更改.

When I created a module-level variable with __ and tried to access it inside a method of a class (using global keyword) the name-mangling occured.

让我展示一个例子:

__test = 'asd'  # module level variable with __


class TestClass(object):
    def test(self):
        global __test
        print(__test)  # trying to access this variable


a = TestClass()
a.test()

口译员提出了一个错误:

Interpreter raised an error:

NameError:未定义名称'_TestClass__test'

因此我们可以看到它试图将 __ test 命名为 _TestClass__test .

So as we can see it tried to name-mangle __test into _TestClass__test.

我认为名称处理只能用于类变量(当我使用 self 或类名访问它们时).

I thought that name-mangling should be used only for class variables (when I access them with self or class name).

这是我不知道的明确定义的行为，还是某种Python错误?

Is it a well-defined behaviour that I have not be aware of or it is some kind of Python bug?

我在CPython 3.5上进行了测试

I tested it on CPython 3.5

推荐答案

任何标识符，格式为 __ spam (至少两个前划线，在文本上最多替换一个结尾的下划线) _classname__spam ，其中 classname 是当前的类名，其中前导下划线被去除.这种处理不加考虑到标识符的句法位置，只要它出现在类的定义之内.

Any identifier of the form __spam (at least two leading underscores, at most one trailing underscore) is textually replaced with _classname__spam, where classname is the current class name with leading underscore(s) stripped. This mangling is done without regard to the syntactic position of the identifier, as long as it occurs within the definition of a class.

(来自 Python文档，重点是我的

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