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86 lines
2.3 KiB
86 lines
2.3 KiB
# -*- python -*-
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#
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# $Id: im_weakref.py,v 1.1 2011-06-08 15:50:07 wirawan Exp $
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#
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# wpylib.py.im_weakref
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# Created: 20110607
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# Wirawan Purwanto
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#
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# Advanced hack tools for python: weakref proxy class for instance-method.
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#
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"""
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wpylib.py.im_weakref
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Complement of weakref's weak reference for an instance method
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(whether bound or unbound).
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Original-source: Linux Screen Reader project
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Copied-from: http://mindtrove.info/python-weak-references/
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Date: 20110607
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"""
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import weakref, new
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class im_ref(object):
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'''
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Our own proxy object which enables weak references to bound and unbound
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methods and arbitrary callables. Pulls information about the function,
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class, and instance out of a bound method. Stores a weak reference to the
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instance to support garbage collection.
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@organization: IBM Corporation
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@copyright: Copyright (c) 2005, 2006 IBM Corporation
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@license: The BSD License
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'''
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def __init__(self, cb):
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try:
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try:
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self.inst = weakref.ref(cb.im_self)
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except TypeError:
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self.inst = None
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self.func = cb.im_func
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self.klass = cb.im_class
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except AttributeError:
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self.inst = None
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self.func = cb.im_func
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self.klass = None
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def __call__(self, *args, **kwargs):
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'''
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Proxy for a call to the weak referenced object. Take arbitrary params to
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pass to the callable.
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@raise ReferenceError: When the weak reference refers to a dead object
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'''
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if self.inst is not None and self.inst() is None:
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raise ReferenceError
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elif self.inst is not None:
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# build a new instance method with a strong reference to the instance
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mtd = new.instancemethod(self.func, self.inst(), self.klass)
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else:
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# not a bound method, just return the func
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mtd = self.func
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# invoke the callable and return the result
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return mtd(*args, **kwargs)
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def __eq__(self, other):
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'''
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Compare the held function and instance with that held by another proxy.
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@param other: Another proxy object
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@type other: L{Proxy}
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@return: Whether this func/inst pair is equal to the one in the other
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proxy object or not
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@rtype: boolean
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'''
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try:
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return self.func == other.func and self.inst() == other.inst()
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except Exception:
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return False
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def __ne__(self, other):
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'''
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Inverse of __eq__.
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'''
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return not self.__eq__(other)
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