Private/Public dispatch decorators in Python

private.py

import inspect
from functools import wraps

def privatemethod(func): 
  """decorator for making an instance method private by dispatching on whether the name 'self' in the local namespace of the calling frame is a reference to the same object as the first positional argument (the self argument when invoking an instance method.) the decorated function will have a 'public' member which is a decorator for specifying an alternate implementation to dispatch calls from outside of the instance."""
  pubfunc = None
  privfunc = func

  @wraps(func)
  def func_wrapper(*args, **kwargs):
    """decorator wrapper function which checks whether the calling frames 'self' refers to the same instance as the first argument. if the check fails, by default an exception is thrown, but this can be overridden by providing an alternate public implementation (see privatemethod.public decorator)."""
    nonlocal pubfunc
    nonlocal privfunc
    outer_frame = inspect.stack()[1][0]
    if 'self' not in outer_frame.f_locals or outer_frame.f_locals['self'] is not args[0]:
      if pubfunc is None:
        raise Exception('%s.%s is a private method' % (args[0].__class__.__name__, func.__name__))
      else:
        return pubfunc(*args, **kwargs)
    else:
      return privfunc(*args, **kwargs)

    def publicdecorator(secondfunc):
    """A decorator for providing a public implementation of the method decorated by @privatemethod, which by default will throw an exception if called from anywhere other than a method of the same instance."""
    nonlocal pubfunc
    pubfunc = secondfunc
    return func_wrapper
  
  func_wrapper.public = publicdecorator
  return func_wrapper