class LazyLoadProxy(object): """ Modified from """ __slots__ = ["_obj_fn", "__weakref__", "__proxy_storage"] def __init__(self, fn, storage=None): object.__setattr__(self, "_obj_fn", fn) object.__setattr__(self, "__proxy_storage", storage) # # proxying (special cases) # def __getattribute__(self, name): return getattr(object.__getattribute__(self, "_obj_fn")(), name) def __delattr__(self, name): delattr(object.__getattribute__(self, "_obj_fn")(), name) def __setattr__(self, name, value): setattr(object.__getattribute__(self, "_obj_fn")(), name, value) def __getitem__(self, index): return object.__getattribute__(self, "_obj_fn")().__getitem__(index) def __nonzero__(self): return bool(object.__getattribute__(self, "_obj_fn")()) def __str__(self): return str(object.__getattribute__(self, "_obj_fn")()) def __repr__(self): return repr(object.__getattribute__(self, "_obj_fn")()) def __len__(self): return len(object.__getattribute__(self, "_obj_fn")()) # # factories # _special_names = [ '__abs__', '__add__', '__and__', '__call__', '__cmp__', '__coerce__', '__contains__', '__delitem__', '__delslice__', '__div__', '__divmod__', '__eq__', '__float__', '__floordiv__', '__ge__', #'__getitem__', '__getslice__', '__gt__', '__hash__', '__hex__', '__iadd__', '__iand__', '__idiv__', '__idivmod__', '__ifloordiv__', '__ilshift__', '__imod__', '__imul__', '__int__', '__invert__', '__ior__', '__ipow__', '__irshift__', '__isub__', '__iter__', '__itruediv__', '__ixor__', '__le__', #'__len__', '__long__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rfloorfiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setitem__', '__setslice__', '__sub__', '__truediv__', '__xor__', 'next', ] @classmethod def _create_class_proxy(cls, theclass): """creates a proxy for the given class""" def make_method(name): def method(self, *args, **kw): return getattr(object.__getattribute__(self, "_obj_fn")(), name)(*args, **kw) return method namespace = {} for name in cls._special_names: if hasattr(theclass, name): namespace[name] = make_method(name) return type("%s(%s)" % (cls.__name__, theclass.__name__), (cls,), namespace) def __new__(cls, obj, *args, **kwargs): """ creates an proxy instance referencing `obj`. (obj, *args, **kwargs) are passed to this class' __init__, so deriving classes can define an __init__ method of their own. note: _class_proxy_cache is unique per deriving class (each deriving class must hold its own cache) """ try: cache = cls.__dict__["_class_proxy_cache"] except KeyError: cls._class_proxy_cache = cache = {} try: theclass = cache[obj.__class__] except KeyError: cache[obj.__class__] = theclass = cls._create_class_proxy(obj.__class__) ins = object.__new__(theclass) theclass.__init__(ins, obj, *args, **kwargs) return ins class Proxy(LazyLoadProxy): def __init__(self, obj): super(Proxy, self).__init__(lambda: obj)