Chain class with special-casing for __call__, which __getattr__ won't handle (same with __getattribute__)

chain_v2.py

"""
Why is __call__ a special case?

https://docs.python.org/3.4/reference/datamodel.html#object.__getattribute__
> Note: This method may still be bypassed when looking up special methods as the result of implicit invocation via language syntax or built-in functions. See Special method lookup.
> In addition to bypassing any instance attributes in the interest of correctness, implicit special method lookup generally also bypasses the __getattribute__() method even of the object’s metaclass
"""


class Chain(object):
    def __init__(self, objs):
        # Private to avoid clashes when we setattr after compiling
        self.__objs = objs
        self.__call_partial = None

    def __compile(self, method):
        _next = noop
        for obj in reversed(self.__objs):
            func = getattr(obj, method, None)
            if func:
                _next = functools.partial(func, _next)
        return _next

    def __getattr__(self, name):
        # Bind the compiled partial to self so we avoid
        # __getattr__ overhead on the next call
        func = self.__compile(name)
        setattr(self, name, func)
        return func

    def __call__(self, *args, **kwargs):
        '''special case because __getattr__ does not handle __call__'''
        if not self.__call_partial:
            self.__call_partial = self.__compile('__call__')
        return self.__call_partial(*args, **kwargs)