class - Private members in Python

Question

How can I make methods and data members private in Python? Or doesn't Python support private members?

Answer 1

9.6. Private Variables

“Private” instance variables that cannot be accessed except from inside an object, don’t exist in Python. However, there is a convention that is followed by most Python code: a name prefixed with an underscore (e.g. _spam) should be treated as a non-public part of the API (whether it is a function, a method or a data member). It should be considered an implementation detail and subject to change without notice.

Since there is a valid use-case for class-private members (namely to avoid name clashes of names with names defined by subclasses), there is limited support for such a mechanism, called name mangling. 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.

So, for example,

class Test:
    def __private_symbol(self):
        pass
    def normal_symbol(self):
        pass

print dir(Test)

will output:

['_Test__private_symbol', 
'__doc__', 
'__module__', 
'normal_symbol']

__private_symbol should be considered a private method, but it would still be accessible through _Test__private_symbol.