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Re: Nice solution wanted: Hide internal interfaces

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On Tue, Oct 30, 2012 at 3:33 AM, Johannes Bauer <dfnsonfsduifb@gmx.de> wrote:
> Hi there,
>
> I'm currently looking for a good solution to the following problem: I
> have two classes A and B, which interact with each other and which
> interact with the user. Instances of B are always created by A.
>
> Now I want A to call some private methods of B and vice versa (i.e. what
> C++ "friends" are), but I want to make it hard for the user to call
> these private methods.

The usual convention for private methods is a leading underscore on the name:

class A:
	def foo(self):
		print("Fooing!")
	def _bar(self):
		print("Only my friends may bar me.")

It's only a convention, though; it doesn't make it "hard" to call
them, it just sends the message "this is private, I don't promise that
it'll be stable across versions".

Incidentally, you may want to use a nested class, if the definition of
B is entirely dependent on A. Something like this:

class A:
	class B:
		def _asdf(self,newval=None):
			if newval is not None: self._val=newval
			return self._val
		def _qwer(self,parent):
			parent._bar("My value is: "+self._val)
	def foo(self):
		self.b=self.B()
		self.b._asdf("Hello, world!")
		self.b._qwer(self)
	def _bar(self,msg):
		print("Message from internal: "+msg)

ChrisA

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Nice solution wanted: Hide internal interfaces Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-10-29 17:33 +0100
  Re: Nice solution wanted: Hide internal interfaces andrea crotti <andrea.crotti.0@gmail.com> - 2012-10-29 16:41 +0000
  Re: Nice solution wanted: Hide internal interfaces Benjamin Kaplan <benjamin.kaplan@case.edu> - 2012-10-29 09:41 -0700
  Re: Nice solution wanted: Hide internal interfaces Chris Angelico <rosuav@gmail.com> - 2012-10-30 03:47 +1100
    Re: Nice solution wanted: Hide internal interfaces Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-10-29 17:58 +0100
      Re: Nice solution wanted: Hide internal interfaces Paul Rubin <no.email@nospam.invalid> - 2012-10-29 10:03 -0700
      Re: Nice solution wanted: Hide internal interfaces Grant Edwards <invalid@invalid.invalid> - 2012-10-29 18:00 +0000
      Re: Nice solution wanted: Hide internal interfaces Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-29 13:09 -0600
  Re: Nice solution wanted: Hide internal interfaces Grant Edwards <invalid@invalid.invalid> - 2012-10-29 16:52 +0000
    Re: Nice solution wanted: Hide internal interfaces Johannes Bauer <dfnsonfsduifb@gmx.de> - 2012-10-29 18:01 +0100
      Re: Nice solution wanted: Hide internal interfaces Peter Otten <__peter__@web.de> - 2012-10-29 18:17 +0100
  Re: Nice solution wanted: Hide internal interfaces Peter Otten <__peter__@web.de> - 2012-10-29 18:06 +0100
  Re: Nice solution wanted: Hide internal interfaces Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-10-29 22:37 +0000
  Re: Nice solution wanted: Hide internal interfaces alex23 <wuwei23@gmail.com> - 2012-10-29 18:37 -0700
    Re: Nice solution wanted: Hide internal interfaces andrea crotti <andrea.crotti.0@gmail.com> - 2012-10-30 14:15 +0000

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