#!/usr/local/bin/python2
import functools
import inspect

class C(object):
  def __init__(self):
    print "init"
  def _a(self):
    print "_a"
  def b(self):
    print "b"

class ExtendableFunction(object):
    def __init__(self, base):
        self._base = base
        self._pre_hooks = []
        self._post_hooks = []

    def __call__(self):
        self.snapshot()

    @property
    def pre_hooks(self):
        return self._pre_hooks

    @property
    def post_hooks(self):
        return self._post_hooks

    @property
    def snapshot(self):
        base = self._base
        pre_hooks = self._pre_hooks[:]
        post_hooks = self._post_hooks[:]
        def extended_func(*args, **kwargs):
            for hook in pre_hooks:
                hook(*args, **kwargs)
            result = base(*args, **kwargs)
            for hook in post_hooks:
                hook(*args, **kwargs)
            return result
        return extended_func

    @classmethod
    def override(cls, obj):
        for name, value in inspect.getmembers(obj, inspect.ismethod):
            if name[0] != '_':
                setattr(obj, name, functools.update_wrapper(cls(value), value))

c = C()
c._a()
c.b()
ExtendableFunction.override(c)
print c.__init__.pre_hooks