Private functions and inheritance

[Maciej Bliziński]

Hello,

I've come across something that I don't quite understand about
Python's inheritance. Consider the following code snippet:

class A(object):
    def call_bar(self): return self.bar()
    def call___bar(self): return self.__bar()
    def __bar(self): return "A::__bar()"
    def bar(self): return "A::bar()"

class B(A):
    def __bar(self): return "B::__bar()"
    def bar(self): return "B::bar()"

b = B()
print "calling B::call_bar():", b.call_bar()
print "calling B::call___bar():", b.call___bar()

The result is:

calling B::call_bar(): B::bar()
calling B::call___bar(): A::__bar()

In the latter case, it calls the base class' implementation. It
probably goes along with Python's spec, but I found it surprising. I
don't want to expose the __bar() function outside, but on the other
hand i want to defer its implementation to a subclass. It seems like I
need to make it public, doesn't it?