Python - Multiple "private" implementations for a class

Question

I have a public class which the module exports, and 3 implementations of it.

At certain points in the program, the implementation used will be changed dynamically, something along the lines of:

class PublicClass(object):

  _IMPLEMENTATION_TO_USE = _Imp1
  def func1(self, arg1): 
    _IMPLEMENTATION_TO_USE.func1(arg1)

class _Imp1(PublicClass):
  def func1(self, arg1): pass

class _Imp2(PublicClass):
  def func1(self, arg1): pass

What's the best (Pythonic) way of achieving it?

Answer 1

Instead of composition, you could consider using a Abstract Base Class, with three different subclasses. In python, duck typing is favoured over explicitly checking types.