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wrappers.py
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import os import sys import functools import operator import weakref import inspect PY2 = sys.version_info[0] == 2 if PY2: string_types = basestring, else: string_types = str, def with_metaclass(meta, *bases): """Create a base class with a metaclass.""" return meta("NewBase", bases, {}) class _ObjectProxyMethods(object): # We use properties to override the values of __module__ and # __doc__. If we add these in ObjectProxy, the derived class # __dict__ will still be setup to have string variants of these # attributes and the rules of descriptors means that they appear to # take precedence over the properties in the base class. To avoid # that, we copy the properties into the derived class type itself # via a meta class. In that way the properties will always take # precedence. @property def __module__(self): return self.__wrapped__.__module__ @__module__.setter def __module__(self, value): self.__wrapped__.__module__ = value @property def __doc__(self): return self.__wrapped__.__doc__ @__doc__.setter def __doc__(self, value): self.__wrapped__.__doc__ = value # We similar use a property for __dict__. We need __dict__ to be # explicit to ensure that vars() works as expected. @property def __dict__(self): return self.__wrapped__.__dict__ # Need to also propagate the special __weakref__ attribute for case # where decorating classes which will define this. If do not define # it and use a function like inspect.getmembers() on a decorator # class it will fail. This can't be in the derived classes. @property def __weakref__(self): return self.__wrapped__.__weakref__ class _ObjectProxyMetaType(type): def __new__(cls, name, bases, dictionary): # Copy our special properties into the class so that they # always take precedence over attributes of the same name added # during construction of a derived class. This is to save # duplicating the implementation for them in all derived classes. dictionary.update(vars(_ObjectProxyMethods)) return type.__new__(cls, name, bases, dictionary) class ObjectProxy(with_metaclass(_ObjectProxyMetaType)): __slots__ = '__wrapped__' def __init__(self, wrapped): object.__setattr__(self, '__wrapped__', wrapped) # Python 3.2+ has the __qualname__ attribute, but it does not # allow it to be overridden using a property and it must instead # be an actual string object instead. try: object.__setattr__(self, '__qualname__', wrapped.__qualname__) except AttributeError: pass # Python 3.10 onwards also does not allow itself to be overridden # using a property and it must instead be set explicitly. try: object.__setattr__(self, '__annotations__', wrapped.__annotations__) except AttributeError: pass @property def __name__(self): return self.__wrapped__.__name__ @__name__.setter def __name__(self, value): self.__wrapped__.__name__ = value @property def __class__(self): return self.__wrapped__.__class__ @__class__.setter def __class__(self, value): self.__wrapped__.__class__ = value def __dir__(self): return dir(self.__wrapped__) def __str__(self): return str(self.__wrapped__) if not PY2: def __bytes__(self): return bytes(self.__wrapped__) def __repr__(self): return '<{} at 0x{:x} for {} at 0x{:x}>'.format( type(self).__name__, id(self), type(self.__wrapped__).__name__, id(self.__wrapped__)) def __reversed__(self): return reversed(self.__wrapped__) if not PY2: def __round__(self): return round(self.__wrapped__) if sys.hexversion >= 0x03070000: def __mro_entries__(self, bases): return (self.__wrapped__,) def __lt__(self, other): return self.__wrapped__ < other def __le__(self, other): return self.__wrapped__ <= other def __eq__(self, other): return self.__wrapped__ == other def __ne__(self, other): return self.__wrapped__ != other def __gt__(self, other): return self.__wrapped__ > other def __ge__(self, other): return self.__wrapped__ >= other def __hash__(self): return hash(self.__wrapped__) def __nonzero__(self): return bool(self.__wrapped__) def __bool__(self): return bool(self.__wrapped__) def __setattr__(self, name, value): if name.startswith('_self_'): object.__setattr__(self, name, value) elif name == '__wrapped__': object.__setattr__(self, name, value) try: object.__delattr__(self, '__qualname__') except AttributeError: pass try: object.__setattr__(self, '__qualname__', value.__qualname__) except AttributeError: pass try: object.__delattr__(self, '__annotations__') except AttributeError: pass try: object.__setattr__(self, '__annotations__', value.__annotations__) except AttributeError: pass elif name == '__qualname__': setattr(self.__wrapped__, name, value) object.__setattr__(self, name, value) elif name == '__annotations__': setattr(self.__wrapped__, name, value) object.__setattr__(self, name, value) elif hasattr(type(self), name): object.__setattr__(self, name, value) else: setattr(self.__wrapped__, name, value) def __getattr__(self, name): # If we are being to lookup '__wrapped__' then the # '__init__()' method cannot have been called. if name == '__wrapped__': raise ValueError('wrapper has not been initialised') return getattr(self.__wrapped__, name) def __delattr__(self, name): if name.startswith('_self_'): object.__delattr__(self, name) elif name == '__wrapped__': raise TypeError('__wrapped__ must be an object') elif name == '__qualname__': object.__delattr__(self, name) delattr(self.__wrapped__, name) elif hasattr(type(self), name): object.__delattr__(self, name) else: delattr(self.__wrapped__, name) def __add__(self, other): return self.__wrapped__ + other def __sub__(self, other): return self.__wrapped__ - other def __mul__(self, other): return self.__wrapped__ * other def __div__(self, other): return operator.div(self.__wrapped__, other) def __truediv__(self, other): return operator.truediv(self.__wrapped__, other) def __floordiv__(self, other): return self.__wrapped__ // other def __mod__(self, other): return self.__wrapped__ % other def __divmod__(self, other): return divmod(self.__wrapped__, other) def __pow__(self, other, *args): return pow(self.__wrapped__, other, *args) def __lshift__(self, other): return self.__wrapped__ << other def __rshift__(self, other): return self.__wrapped__ >> other def __and__(self, other): return self.__wrapped__ & other def __xor__(self, other): return self.__wrapped__ ^ other def __or__(self, other): return self.__wrapped__ | other def __radd__(self, other): return other + self.__wrapped__ def __rsub__(self, other): return other - self.__wrapped__ def __rmul__(self, other): return other * self.__wrapped__ def __rdiv__(self, other): return operator.div(other, self.__wrapped__) def __rtruediv__(self, other): return operator.truediv(other, self.__wrapped__) def __rfloordiv__(self, other): return other // self.__wrapped__ def __rmod__(self, other): return other % self.__wrapped__ def __rdivmod__(self, other): return divmod(other, self.__wrapped__) def __rpow__(self, other, *args): return pow(other, self.__wrapped__, *args) def __rlshift__(self, other): return other << self.__wrapped__ def __rrshift__(self, other): return other >> self.__wrapped__ def __rand__(self, other): return other & self.__wrapped__ def __rxor__(self, other): return other ^ self.__wrapped__ def __ror__(self, other): return other | self.__wrapped__ def __iadd__(self, other): self.__wrapped__ += other return self def __isub__(self, other): self.__wrapped__ -= other return self def __imul__(self, other): self.__wrapped__ *= other return self def __idiv__(self, other): self.__wrapped__ = operator.idiv(self.__wrapped__, other) return self def __itruediv__(self, other): self.__wrapped__ = operator.itruediv(self.__wrapped__, other) return self def __ifloordiv__(self, other): self.__wrapped__ //= other return self def __imod__(self, other): self.__wrapped__ %= other return self def __ipow__(self, other): self.__wrapped__ **= other return self def __ilshift__(self, other): self.__wrapped__ <<= other return self def __irshift__(self, other): self.__wrapped__ >>= other return self def __iand__(self, other): self.__wrapped__ &= other return self def __ixor__(self, other): self.__wrapped__ ^= other return self def __ior__(self, other): self.__wrapped__ |= other return self def __neg__(self): return -self.__wrapped__ def __pos__(self): return +self.__wrapped__ def __abs__(self): return abs(self.__wrapped__) def __invert__(self): return ~self.__wrapped__ def __int__(self): return int(self.__wrapped__) def __long__(self): return long(self.__wrapped__) def __float__(self): return float(self.__wrapped__) def __complex__(self): return complex(self.__wrapped__) def __oct__(self): return oct(self.__wrapped__) def __hex__(self): return hex(self.__wrapped__) def __index__(self): return operator.index(self.__wrapped__) def __len__(self): return len(self.__wrapped__) def __contains__(self, value): return value in self.__wrapped__ def __getitem__(self, key): return self.__wrapped__[key] def __setitem__(self, key, value): self.__wrapped__[key] = value def __delitem__(self, key): del self.__wrapped__[key] def __getslice__(self, i, j): return self.__wrapped__[i:j] def __setslice__(self, i, j, value): self.__wrapped__[i:j] = value def __delslice__(self, i, j): del self.__wrapped__[i:j] def __enter__(self): return self.__wrapped__.__enter__() def __exit__(self, *args, **kwargs): return self.__wrapped__.__exit__(*args, **kwargs) def __iter__(self): return iter(self.__wrapped__) def __copy__(self): raise NotImplementedError('object proxy must define __copy__()') def __deepcopy__(self, memo): raise NotImplementedError('object proxy must define __deepcopy__()') def __reduce__(self): raise NotImplementedError( 'object proxy must define __reduce_ex__()') def __reduce_ex__(self, protocol): raise NotImplementedError( 'object proxy must define __reduce_ex__()') class CallableObjectProxy(ObjectProxy): def __call__(*args, **kwargs): def _unpack_self(self, *args): return self, args self, args = _unpack_self(*args) return self.__wrapped__(*args, **kwargs) class PartialCallableObjectProxy(ObjectProxy): def __init__(*args, **kwargs): def _unpack_self(self, *args): return self, args self, args = _unpack_self(*args) if len(args) < 1: raise TypeError('partial type takes at least one argument') wrapped, args = args[0], args[1:] if not callable(wrapped): raise TypeError('the first argument must be callable') super(PartialCallableObjectProxy, self).__init__(wrapped) self._self_args = args self._self_kwargs = kwargs def __call__(*args, **kwargs): def _unpack_self(self, *args): return self, args self, args = _unpack_self(*args) _args = self._self_args + args _kwargs = dict(self._self_kwargs) _kwargs.update(kwargs) return self.__wrapped__(*_args, **_kwargs) class _FunctionWrapperBase(ObjectProxy): __slots__ = ('_self_instance', '_self_wrapper', '_self_enabled', '_self_binding', '_self_parent') def __init__(self, wrapped, instance, wrapper, enabled=None, binding='function', parent=None): super(_FunctionWrapperBase, self).__init__(wrapped) object.__setattr__(self, '_self_instance', instance) object.__setattr__(self, '_self_wrapper', wrapper) object.__setattr__(self, '_self_enabled', enabled) object.__setattr__(self, '_self_binding', binding) object.__setattr__(self, '_self_parent', parent) def __get__(self, instance, owner): # This method is actually doing double duty for both unbound and # bound derived wrapper classes. It should possibly be broken up # and the distinct functionality moved into the derived classes. # Can't do that straight away due to some legacy code which is # relying on it being here in this base class. # # The distinguishing attribute which determines whether we are # being called in an unbound or bound wrapper is the parent # attribute. If binding has never occurred, then the parent will # be None. # # First therefore, is if we are called in an unbound wrapper. In # this case we perform the binding. # # We have one special case to worry about here. This is where we # are decorating a nested class. In this case the wrapped class # would not have a __get__() method to call. In that case we # simply return self. # # Note that we otherwise still do binding even if instance is # None and accessing an unbound instance method from a class. # This is because we need to be able to later detect that # specific case as we will need to extract the instance from the # first argument of those passed in. if self._self_parent is None: if not inspect.isclass(self.__wrapped__): descriptor = self.__wrapped__.__get__(instance, owner) return self.__bound_function_wrapper__(descriptor, instance, self._self_wrapper, self._self_enabled, self._self_binding, self) return self # Now we have the case of binding occurring a second time on what # was already a bound function. In this case we would usually # return ourselves again. This mirrors what Python does. # # The special case this time is where we were originally bound # with an instance of None and we were likely an instance # method. In that case we rebind against the original wrapped # function from the parent again. if self._self_instance is None and self._self_binding == 'function': descriptor = self._self_parent.__wrapped__.__get__( instance, owner) return self._self_parent.__bound_function_wrapper__( descriptor, instance, self._self_wrapper, self._self_enabled, self._self_binding, self._self_parent) return self def __call__(*args, **kwargs): def _unpack_self(self, *args): return self, args self, args = _unpack_self(*args) # If enabled has been specified, then evaluate it at this point # and if the wrapper is not to be executed, then simply return # the bound function rather than a bound wrapper for the bound # function. When evaluating enabled, if it is callable we call # it, otherwise we evaluate it as a boolean. if self._self_enabled is not None: if callable(self._self_enabled): if not self._self_enabled(): return self.__wrapped__(*args, **kwargs) elif not self._self_enabled: return self.__wrapped__(*args, **kwargs) # This can occur where initial function wrapper was applied to # a function that was already bound to an instance. In that case # we want to extract the instance from the function and use it. if self._self_binding in ('function', 'classmethod'): if self._self_instance is None: instance = getattr(self.__wrapped__, '__self__', None) if instance is not None: return self._self_wrapper(self.__wrapped__, instance, args, kwargs) # This is generally invoked when the wrapped function is being # called as a normal function and is not bound to a class as an # instance method. This is also invoked in the case where the # wrapped function was a method, but this wrapper was in turn # wrapped using the staticmethod decorator. return self._self_wrapper(self.__wrapped__, self._self_instance, args, kwargs) def __set_name__(self, owner, name): # This is a special method use to supply information to # descriptors about what the name of variable in a class # definition is. Not wanting to add this to ObjectProxy as not # sure of broader implications of doing that. Thus restrict to # FunctionWrapper used by decorators. if hasattr(self.__wrapped__, "__set_name__"): self.__wrapped__.__set_name__(owner, name) def __instancecheck__(self, instance): # This is a special method used by isinstance() to make checks # instance of the `__wrapped__`. return isinstance(instance, self.__wrapped__) def __subclasscheck__(self, subclass): # This is a special method used by issubclass() to make checks # about inheritance of classes. We need to upwrap any object # proxy. Not wanting to add this to ObjectProxy as not sure of # broader implications of doing that. Thus restrict to # FunctionWrapper used by decorators. if hasattr(subclass, "__wrapped__"): return issubclass(subclass.__wrapped__, self.__wrapped__) else: return issubclass(subclass, self.__wrapped__) class BoundFunctionWrapper(_FunctionWrapperBase): def __call__(*args, **kwargs): def _unpack_self(self, *args): return self, args self, args = _unpack_self(*args) # If enabled has been specified, then evaluate it at this point # and if the wrapper is not to be executed, then simply return # the bound function rather than a bound wrapper for the bound # function. When evaluating enabled, if it is callable we call # it, otherwise we evaluate it as a boolean. if self._self_enabled is not None: if callable(self._self_enabled): if not self._self_enabled(): return self.__wrapped__(*args, **kwargs) elif not self._self_enabled: return self.__wrapped__(*args, **kwargs) # We need to do things different depending on whether we are # likely wrapping an instance method vs a static method or class # method. if self._self_binding == 'function': if self._self_instance is None: # This situation can occur where someone is calling the # instancemethod via the class type and passing the instance # as the first argument. We need to shift the args before # making the call to the wrapper and effectively bind the # instance to the wrapped function using a partial so the # wrapper doesn't see anything as being different. if not args: raise TypeError('missing 1 required positional argument') instance, args = args[0], args[1:] wrapped = PartialCallableObjectProxy(self.__wrapped__, instance) return self._self_wrapper(wrapped, instance, args, kwargs) return self._self_wrapper(self.__wrapped__, self._self_instance, args, kwargs) else: # As in this case we would be dealing with a classmethod or # staticmethod, then _self_instance will only tell us whether # when calling the classmethod or staticmethod they did it via an # instance of the class it is bound to and not the case where # done by the class type itself. We thus ignore _self_instance # and use the __self__ attribute of the bound function instead. # For a classmethod, this means instance will be the class type # and for a staticmethod it will be None. This is probably the # more useful thing we can pass through even though we loose # knowledge of whether they were called on the instance vs the # class type, as it reflects what they have available in the # decoratored function. instance = getattr(self.__wrapped__, '__self__', None) return self._self_wrapper(self.__wrapped__, instance, args, kwargs) class FunctionWrapper(_FunctionWrapperBase): __bound_function_wrapper__ = BoundFunctionWrapper def __init__(self, wrapped, wrapper, enabled=None): # What it is we are wrapping here could be anything. We need to # try and detect specific cases though. In particular, we need # to detect when we are given something that is a method of a # class. Further, we need to know when it is likely an instance # method, as opposed to a class or static method. This can # become problematic though as there isn't strictly a fool proof # method of knowing. # # The situations we could encounter when wrapping a method are: # # 1. The wrapper is being applied as part of a decorator which # is a part of the class definition. In this case what we are # given is the raw unbound function, classmethod or staticmethod # wrapper objects. # # The problem here is that we will not know we are being applied # in the context of the class being set up. This becomes # important later for the case of an instance method, because in # that case we just see it as a raw function and can't # distinguish it from wrapping a normal function outside of # a class context. # # 2. The wrapper is being applied when performing monkey # patching of the class type afterwards and the method to be # wrapped was retrieved direct from the __dict__ of the class # type. This is effectively the same as (1) above. # # 3. The wrapper is being applied when performing monkey # patching of the class type afterwards and the method to be # wrapped was retrieved from the class type. In this case # binding will have been performed where the instance against # which the method is bound will be None at that point. # # This case is a problem because we can no longer tell if the # method was a static method, plus if using Python3, we cannot # tell if it was an instance method as the concept of an # unnbound method no longer exists. # # 4. The wrapper is being applied when performing monkey # patching of an instance of a class. In this case binding will # have been perfomed where the instance was not None. # # This case is a problem because we can no longer tell if the # method was a static method. # # Overall, the best we can do is look at the original type of the # object which was wrapped prior to any binding being done and # see if it is an instance of classmethod or staticmethod. In # the case where other decorators are between us and them, if # they do not propagate the __class__ attribute so that the # isinstance() checks works, then likely this will do the wrong # thing where classmethod and staticmethod are used. # # Since it is likely to be very rare that anyone even puts # decorators around classmethod and staticmethod, likelihood of # that being an issue is very small, so we accept it and suggest # that those other decorators be fixed. It is also only an issue # if a decorator wants to actually do things with the arguments. # # As to not being able to identify static methods properly, we # just hope that that isn't something people are going to want # to wrap, or if they do suggest they do it the correct way by # ensuring that it is decorated in the class definition itself, # or patch it in the __dict__ of the class type. # # So to get the best outcome we can, whenever we aren't sure what # it is, we label it as a 'function'. If it was already bound and # that is rebound later, we assume that it will be an instance # method and try an cope with the possibility that the 'self' # argument it being passed as an explicit argument and shuffle # the arguments around to extract 'self' for use as the instance. if isinstance(wrapped, classmethod): binding = 'classmethod' elif isinstance(wrapped, staticmethod): binding = 'staticmethod' elif hasattr(wrapped, '__self__'): if inspect.isclass(wrapped.__self__): binding = 'classmethod' else: binding = 'function' else: binding = 'function' super(FunctionWrapper, self).__init__(wrapped, None, wrapper, enabled, binding) try: if not os.environ.get('WRAPT_DISABLE_EXTENSIONS'): from ._wrappers import (ObjectProxy, CallableObjectProxy, PartialCallableObjectProxy, FunctionWrapper, BoundFunctionWrapper, _FunctionWrapperBase) except ImportError: pass # Helper functions for applying wrappers to existing functions. def resolve_path(module, name): if isinstance(module, string_types): __import__(module) module = sys.modules[module] parent = module path = name.split('.') attribute = path[0] # We can't just always use getattr() because in doing # that on a class it will cause binding to occur which # will complicate things later and cause some things not # to work. For the case of a class we therefore access # the __dict__ directly. To cope though with the wrong # class being given to us, or a method being moved into # a base class, we need to walk the class hierarchy to # work out exactly which __dict__ the method was defined # in, as accessing it from __dict__ will fail if it was # not actually on the class given. Fallback to using # getattr() if we can't find it. If it truly doesn't # exist, then that will fail. def lookup_attribute(parent, attribute): if inspect.isclass(parent): for cls in inspect.getmro(parent): if attribute in vars(cls): return vars(cls)[attribute] else: return getattr(parent, attribute) else: return getattr(parent, attribute) original = lookup_attribute(parent, attribute) for attribute in path[1:]: parent = original original = lookup_attribute(parent, attribute) return (parent, attribute, original) def apply_patch(parent, attribute, replacement): setattr(parent, attribute, replacement) def wrap_object(module, name, factory, args=(), kwargs={}): (parent, attribute, original) = resolve_path(module, name) wrapper = factory(original, *args, **kwargs) apply_patch(parent, attribute, wrapper) return wrapper # Function for applying a proxy object to an attribute of a class # instance. The wrapper works by defining an attribute of the same name # on the class which is a descriptor and which intercepts access to the # instance attribute. Note that this cannot be used on attributes which # are themselves defined by a property object. class AttributeWrapper(object): def __init__(self, attribute, factory, args, kwargs): self.attribute = attribute self.factory = factory self.args = args self.kwargs = kwargs def __get__(self, instance, owner): value = instance.__dict__[self.attribute] return self.factory(value, *self.args, **self.kwargs) def __set__(self, instance, value): instance.__dict__[self.attribute] = value def __delete__(self, instance): del instance.__dict__[self.attribute] def wrap_object_attribute(module, name, factory, args=(), kwargs={}): path, attribute = name.rsplit('.', 1) parent = resolve_path(module, path)[2] wrapper = AttributeWrapper(attribute, factory, args, kwargs) apply_patch(parent, attribute, wrapper) return wrapper # Functions for creating a simple decorator using a FunctionWrapper, # plus short cut functions for applying wrappers to functions. These are # for use when doing monkey patching. For a more featured way of # creating decorators see the decorator decorator instead. def function_wrapper(wrapper): def _wrapper(wrapped, instance, args, kwargs): target_wrapped = args[0] if instance is None: target_wrapper = wrapper elif inspect.isclass(instance): target_wrapper = wrapper.__get__(None, instance) else: target_wrapper = wrapper.__get__(instance, type(instance)) return FunctionWrapper(target_wrapped, target_wrapper) return FunctionWrapper(wrapper, _wrapper) def wrap_function_wrapper(module, name, wrapper): return wrap_object(module, name, FunctionWrapper, (wrapper,)) def patch_function_wrapper(module, name): def _wrapper(wrapper): return wrap_object(module, name, FunctionWrapper, (wrapper,)) return _wrapper def transient_function_wrapper(module, name): def _decorator(wrapper): def _wrapper(wrapped, instance, args, kwargs): target_wrapped = args[0] if instance is None: target_wrapper = wrapper elif inspect.isclass(instance): target_wrapper = wrapper.__get__(None, instance) else: target_wrapper = wrapper.__get__(instance, type(instance)) def _execute(wrapped, instance, args, kwargs): (parent, attribute, original) = resolve_path(module, name) replacement = FunctionWrapper(original, target_wrapper) setattr(parent, attribute, replacement) try: return wrapped(*args, **kwargs) finally: setattr(parent, attribute, original) return FunctionWrapper(target_wrapped, _execute) return FunctionWrapper(wrapper, _wrapper) return _decorator # A weak function proxy. This will work on instance methods, class # methods, static methods and regular functions. Special treatment is # needed for the method types because the bound method is effectively a # transient object and applying a weak reference to one will immediately # result in it being destroyed and the weakref callback called. The weak # reference is therefore applied to the instance the method is bound to # and the original function. The function is then rebound at the point # of a call via the weak function proxy. def _weak_function_proxy_callback(ref, proxy, callback): if proxy._self_expired: return proxy._self_expired = True # This could raise an exception. We let it propagate back and let # the weakref.proxy() deal with it, at which point it generally # prints out a short error message direct to stderr and keeps going. if callback is not None: callback(proxy) class WeakFunctionProxy(ObjectProxy): __slots__ = ('_self_expired', '_self_instance') def __init__(self, wrapped, callback=None): # We need to determine if the wrapped function is actually a # bound method. In the case of a bound method, we need to keep a # reference to the original unbound function and the instance. # This is necessary because if we hold a reference to the bound # function, it will be the only reference and given it is a # temporary object, it will almost immediately expire and # the weakref callback triggered. So what is done is that we # hold a reference to the instance and unbound function and # when called bind the function to the instance once again and # then call it. Note that we avoid using a nested function for # the callback here so as not to cause any odd reference cycles. _callback = callback and functools.partial( _weak_function_proxy_callback, proxy=self, callback=callback) self._self_expired = False if isinstance(wrapped, _FunctionWrapperBase): self._self_instance = weakref.ref(wrapped._self_instance, _callback) if wrapped._self_parent is not None: super(WeakFunctionProxy, self).__init__( weakref.proxy(wrapped._self_parent, _callback)) else: super(WeakFunctionProxy, self).__init__( weakref.proxy(wrapped, _callback)) return try: self._self_instance = weakref.ref(wrapped.__self__, _callback) super(WeakFunctionProxy, self).__init__( weakref.proxy(wrapped.__func__, _callback)) except AttributeError: self._self_instance = None super(WeakFunctionProxy, self).__init__( weakref.proxy(wrapped, _callback)) def __call__(*args, **kwargs): def _unpack_self(self, *args): return self, args self, args = _unpack_self(*args) # We perform a boolean check here on the instance and wrapped # function as that will trigger the reference error prior to # calling if the reference had expired. instance = self._self_instance and self._self_instance() function = self.__wrapped__ and self.__wrapped__ # If the wrapped function was originally a bound function, for # which we retained a reference to the instance and the unbound # function we need to rebind the function and then call it. If # not just called the wrapped function. if instance is None: return self.__wrapped__(*args, **kwargs) return function.__get__(instance, type(instance))(*args, **kwargs)