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6114679099
* Check the found object for a None value during a contains/has_key lookup. Perhaps it will help the OP who is likely suffering from an occassional GC or threading object deletion after self.data is checked. * Complete the previous patch by removing the unnecessary indirection for weak dict iterators. Makes the code cleaner and more readable.
308 lines
8.0 KiB
Python
308 lines
8.0 KiB
Python
"""Weak reference support for Python.
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This module is an implementation of PEP 205:
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http://python.sourceforge.net/peps/pep-0205.html
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"""
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# Naming convention: Variables named "wr" are weak reference objects;
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# they are called this instead of "ref" to avoid name collisions with
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# the module-global ref() function imported from _weakref.
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import UserDict
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from _weakref import \
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getweakrefcount, \
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getweakrefs, \
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ref, \
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proxy, \
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CallableProxyType, \
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ProxyType, \
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ReferenceType
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from exceptions import ReferenceError
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ProxyTypes = (ProxyType, CallableProxyType)
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__all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
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"WeakKeyDictionary", "ReferenceType", "ProxyType",
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"CallableProxyType", "ProxyTypes", "WeakValueDictionary"]
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class WeakValueDictionary(UserDict.UserDict):
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"""Mapping class that references values weakly.
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Entries in the dictionary will be discarded when no strong
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reference to the value exists anymore
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"""
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# We inherit the constructor without worrying about the input
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# dictionary; since it uses our .update() method, we get the right
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# checks (if the other dictionary is a WeakValueDictionary,
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# objects are unwrapped on the way out, and we always wrap on the
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# way in).
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def __init__(self, *args, **kw):
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UserDict.UserDict.__init__(self, *args, **kw)
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def remove(wr, selfref=ref(self)):
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self = selfref()
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if self is not None:
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del self.data[wr.key]
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self._remove = remove
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def __getitem__(self, key):
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o = self.data[key]()
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if o is None:
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raise KeyError, key
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else:
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return o
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def __contains__(self, key):
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try:
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o = self.data[key]()
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except KeyError:
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return False
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return o is not None
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def has_key(self, key):
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try:
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o = self.data[key]()
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except KeyError:
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return False
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return o is not None
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def __repr__(self):
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return "<WeakValueDictionary at %s>" % id(self)
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def __setitem__(self, key, value):
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self.data[key] = KeyedRef(value, self._remove, key)
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def copy(self):
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new = WeakValueDictionary()
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for key, wr in self.data.items():
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o = wr()
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if o is not None:
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new[key] = o
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return new
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def get(self, key, default=None):
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try:
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wr = self.data[key]
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except KeyError:
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return default
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else:
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o = wr()
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if o is None:
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# This should only happen
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return default
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else:
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return o
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def items(self):
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L = []
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for key, wr in self.data.items():
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o = wr()
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if o is not None:
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L.append((key, o))
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return L
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def iteritems(self):
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for wr in self.data.itervalues():
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value = wr()
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if value is not None:
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yield wr.key, value
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def iterkeys(self):
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return self.data.iterkeys()
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def __iter__(self):
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return self.data.iterkeys()
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def itervalues(self):
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for wr in self.data.itervalues():
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obj = wr()
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if obj is not None:
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yield obj
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def popitem(self):
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while 1:
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key, wr = self.data.popitem()
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o = wr()
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if o is not None:
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return key, o
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def pop(self, key, *args):
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try:
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o = self.data.pop(key)()
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except KeyError:
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if args:
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return args[0]
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raise
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if o is None:
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raise KeyError, key
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else:
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return o
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def setdefault(self, key, default=None):
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try:
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wr = self.data[key]
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except KeyError:
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self.data[key] = KeyedRef(default, self._remove, key)
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return default
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else:
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return wr()
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def update(self, dict=None, **kwargs):
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d = self.data
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if dict is not None:
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if not hasattr(dict, "items"):
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dict = type({})(dict)
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for key, o in dict.items():
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d[key] = KeyedRef(o, self._remove, key)
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if len(kwargs):
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self.update(kwargs)
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def values(self):
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L = []
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for wr in self.data.values():
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o = wr()
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if o is not None:
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L.append(o)
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return L
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class KeyedRef(ref):
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"""Specialized reference that includes a key corresponding to the value.
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This is used in the WeakValueDictionary to avoid having to create
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a function object for each key stored in the mapping. A shared
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callback object can use the 'key' attribute of a KeyedRef instead
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of getting a reference to the key from an enclosing scope.
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"""
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__slots__ = "key",
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def __new__(type, ob, callback, key):
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self = ref.__new__(type, ob, callback)
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self.key = key
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return self
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def __init__(self, ob, callback, key):
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super(KeyedRef, self).__init__(ob, callback)
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class WeakKeyDictionary(UserDict.UserDict):
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""" Mapping class that references keys weakly.
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Entries in the dictionary will be discarded when there is no
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longer a strong reference to the key. This can be used to
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associate additional data with an object owned by other parts of
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an application without adding attributes to those objects. This
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can be especially useful with objects that override attribute
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accesses.
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"""
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def __init__(self, dict=None):
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self.data = {}
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def remove(k, selfref=ref(self)):
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self = selfref()
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if self is not None:
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del self.data[k]
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self._remove = remove
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if dict is not None: self.update(dict)
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def __delitem__(self, key):
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del self.data[ref(key)]
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def __getitem__(self, key):
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return self.data[ref(key)]
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def __repr__(self):
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return "<WeakKeyDictionary at %s>" % id(self)
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def __setitem__(self, key, value):
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self.data[ref(key, self._remove)] = value
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def copy(self):
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new = WeakKeyDictionary()
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for key, value in self.data.items():
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o = key()
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if o is not None:
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new[o] = value
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return new
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def get(self, key, default=None):
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return self.data.get(ref(key),default)
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def has_key(self, key):
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try:
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wr = ref(key)
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except TypeError:
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return 0
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return wr in self.data
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def __contains__(self, key):
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try:
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wr = ref(key)
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except TypeError:
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return 0
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return wr in self.data
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def items(self):
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L = []
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for key, value in self.data.items():
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o = key()
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if o is not None:
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L.append((o, value))
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return L
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def iteritems(self):
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for wr, value in self.data.iteritems():
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key = wr()
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if key is not None:
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yield key, value
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def iterkeys(self):
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for wr in self.data.iterkeys():
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obj = wr()
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if obj is not None:
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yield obj
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def __iter__(self):
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return self.iterkeys()
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def itervalues(self):
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return self.data.itervalues()
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def keys(self):
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L = []
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for wr in self.data.keys():
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o = wr()
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if o is not None:
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L.append(o)
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return L
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def popitem(self):
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while 1:
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key, value = self.data.popitem()
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o = key()
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if o is not None:
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return o, value
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def pop(self, key, *args):
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return self.data.pop(ref(key), *args)
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def setdefault(self, key, default=None):
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return self.data.setdefault(ref(key, self._remove),default)
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def update(self, dict=None, **kwargs):
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d = self.data
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if dict is not None:
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if not hasattr(dict, "items"):
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dict = type({})(dict)
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for key, value in dict.items():
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d[ref(key, self._remove)] = value
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if len(kwargs):
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self.update(kwargs)
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