python - Python 中的私有(private)变量和方法

Question

这个问题在这里已经有了答案:

关闭 10年前。

Possible Duplicate:
The meaning of a single- and a double-underscore before an object name in Python

对于 Python 中的私有(private)成员和方法，我应该使用 _foo(下划线)还是 __bar(双下划线)？

Answer 1

请注意，Python 中没有“私有(private)方法”之类的东西。双下划线只是名称修饰:

>>> class A(object):
...     def __foo(self):
...         pass
... 
>>> a = A()
>>> A.__dict__.keys()
['__dict__', '_A__foo', '__module__', '__weakref__', '__doc__']
>>> a._A__foo()

因此，__ 前缀在您需要发生重整时很有用，例如不与继承链上或下的名称发生冲突。对于其他用途，单下划线会更好，恕我直言。

编辑，关于 __ 的混淆，PEP-8很清楚:

If your class is intended to be subclassed, and you have attributesthat you do not want subclasses to use, consider naming them withdouble leading underscores and no trailing underscores. This invokesPython's name mangling algorithm, where the name of the class ismangled into the attribute name. This helps avoid attribute namecollisions should subclasses inadvertently contain attributes with thesame name.

Note 3: Not everyone likes name mangling. Try to balance theneed to avoid accidental name clashes with potential use byadvanced callers.

因此，如果您不希望子类意外地重新定义自己的同名方法，请不要使用它。