class LazyLoadProxy(object):
"""
Modified from http://code.activestate.com/recipes/496741-object-proxying/
"""
__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)
