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@ -5,9 +5,11 @@ Provides a way to safely weakref any function, including bound methods (which
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aren't handled by the core weakref module).
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"""
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import weakref, traceback
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import weakref
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import traceback
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def safeRef(target, onDelete = None):
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def safeRef(target, onDelete=None):
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"""Return a *safe* weak reference to a callable target
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target -- the object to be weakly referenced, if it's a
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@ -22,7 +24,9 @@ def safeRef(target, onDelete = None):
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if target.im_self is not None:
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# Turn a bound method into a BoundMethodWeakref instance.
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# Keep track of these instances for lookup by disconnect().
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assert hasattr(target, 'im_func'), """safeRef target %r has im_self, but no im_func, don't know how to create reference"""%( target,)
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assert hasattr(target, 'im_func'), \
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"safeRef target %r has im_self, but no im_func, " \
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"don't know how to create reference" % (target,)
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reference = get_bound_method_weakref(
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target=target,
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onDelete=onDelete
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@ -31,7 +35,8 @@ def safeRef(target, onDelete = None):
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if callable(onDelete):
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return weakref.ref(target, onDelete)
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else:
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return weakref.ref( target )
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return weakref.ref(target)
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class BoundMethodWeakref(object):
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"""'Safe' and reusable weak references to instance methods
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@ -66,10 +71,10 @@ class BoundMethodWeakref(object):
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same BoundMethodWeakref instance.
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"""
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_allInstances = weakref.WeakValueDictionary()
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def __new__( cls, target, onDelete=None, *arguments,**named ):
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def __new__(cls, target, onDelete=None, *arguments, **named):
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"""Create new instance or return current instance
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Basically this method of construction allows us to
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@ -82,16 +87,16 @@ class BoundMethodWeakref(object):
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of already-referenced methods.
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"""
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key = cls.calculateKey(target)
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current =cls._allInstances.get(key)
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current = cls._allInstances.get(key)
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if current is not None:
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current.deletionMethods.append( onDelete)
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current.deletionMethods.append(onDelete)
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return current
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else:
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base = super( BoundMethodWeakref, cls).__new__( cls )
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base = super(BoundMethodWeakref, cls).__new__(cls)
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cls._allInstances[key] = base
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base.__init__( target, onDelete, *arguments,**named)
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base.__init__(target, onDelete, *arguments, **named)
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return base
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def __init__(self, target, onDelete=None):
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"""Return a weak-reference-like instance for a bound method
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@ -111,56 +116,55 @@ class BoundMethodWeakref(object):
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methods = self.deletionMethods[:]
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del self.deletionMethods[:]
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try:
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del self.__class__._allInstances[ self.key ]
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del self.__class__._allInstances[self.key]
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except KeyError:
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pass
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for function in methods:
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try:
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if callable( function ):
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function( self )
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if callable(function):
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function(self)
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except Exception, e:
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try:
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traceback.print_exc()
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except AttributeError:
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print '''Exception during saferef %s cleanup function %s: %s'''%(
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self, function, e
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)
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print "Exception during saferef %s cleanup "
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"function %s: %s" % (self, function, e)
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self.deletionMethods = [onDelete]
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self.key = self.calculateKey( target )
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self.key = self.calculateKey(target)
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self.weakSelf = weakref.ref(target.im_self, remove)
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self.weakFunc = weakref.ref(target.im_func, remove)
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self.selfName = str(target.im_self)
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self.funcName = str(target.im_func.__name__)
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def calculateKey( cls, target ):
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def calculateKey(cls, target):
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"""Calculate the reference key for this reference
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Currently this is a two-tuple of the id()'s of the
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target object and the target function respectively.
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"""
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return (id(target.im_self),id(target.im_func))
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calculateKey = classmethod( calculateKey )
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return (id(target.im_self), id(target.im_func))
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calculateKey = classmethod(calculateKey)
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def __str__(self):
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"""Give a friendly representation of the object"""
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return """%s( %s.%s )"""%(
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return """%s( %s.%s )""" % (
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self.__class__.__name__,
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self.selfName,
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self.funcName,
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)
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__repr__ = __str__
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def __nonzero__( self ):
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def __nonzero__(self):
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"""Whether we are still a valid reference"""
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return self() is not None
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def __cmp__( self, other ):
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def __cmp__(self, other):
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"""Compare with another reference"""
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if not isinstance (other,self.__class__):
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return cmp( self.__class__, type(other) )
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return cmp( self.key, other.key)
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if not isinstance(other, self.__class__):
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return cmp(self.__class__, type(other))
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return cmp(self.key, other.key)
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def __call__(self):
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"""Return a strong reference to the bound method
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@ -179,14 +183,15 @@ class BoundMethodWeakref(object):
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return function.__get__(target)
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return None
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class BoundNonDescriptorMethodWeakref(BoundMethodWeakref):
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"""A specialized BoundMethodWeakref, for platforms where instance methods
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are not descriptors.
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It assumes that the function name and the target attribute name are the
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same, instead of assuming that the function is a descriptor. This approach
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is equally fast, but not 100% reliable because functions can be stored on an
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attribute named differenty than the function's name such as in:
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is equally fast, but not 100% reliable because functions can be stored on
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an attribute named differenty than the function's name such as in:
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class A: pass
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def foo(self): return "foo"
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@ -211,7 +216,7 @@ class BoundNonDescriptorMethodWeakref(BoundMethodWeakref):
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which will be passed a pointer to this object.
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"""
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assert getattr(target.im_self, target.__name__) == target, \
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("method %s isn't available as the attribute %s of %s" %
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("method %s isn't available as the attribute %s of %s" %
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(target, target.__name__, target.im_self))
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super(BoundNonDescriptorMethodWeakref, self).__init__(target, onDelete)
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@ -239,12 +244,14 @@ class BoundNonDescriptorMethodWeakref(BoundMethodWeakref):
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return getattr(target, function.__name__)
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return None
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def get_bound_method_weakref(target, onDelete):
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"""Instantiates the appropiate BoundMethodWeakRef, depending on the details of
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the underlying class method implementation"""
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"""Instantiates the appropiate BoundMethodWeakRef, depending on the
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details of the underlying class method implementation"""
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if hasattr(target, '__get__'):
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# target method is a descriptor, so the default implementation works:
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return BoundMethodWeakref(target=target, onDelete=onDelete)
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else:
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# no luck, use the alternative implementation:
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return BoundNonDescriptorMethodWeakref(target=target, onDelete=onDelete)
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return BoundNonDescriptorMethodWeakref(target=target,
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onDelete=onDelete)
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