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886128f4f8
Someone review this, please! Final releases are getting close, Fred (the weakref guy) won't be around until Tuesday, and the pre-patch code can indeed raise spurious RuntimeErrors in the presence of threads or mutating comparison functions. See the bug report for my confusions: I can't see any reason for why __delitem__ iterated over the keys. The new one-liner implementation is much faster, can't raise RuntimeError, and should be better-behaved in all respects wrt threads. New tests test_weak_keyed_bad_delitem and test_weak_keyed_cascading_deletes fail before this patch. Bugfix candidate for 2.2.3 too, if someone else agrees with this patch.
302 lines
7.5 KiB
Python
302 lines
7.5 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 __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 __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] = ref(value, self.__makeremove(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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return WeakValuedItemIterator(self)
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def iterkeys(self):
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return self.data.iterkeys()
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__iter__ = iterkeys
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def itervalues(self):
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return WeakValuedValueIterator(self)
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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):
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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] = ref(default, self.__makeremove(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):
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d = self.data
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for key, o in dict.items():
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d[key] = ref(o, self.__makeremove(key))
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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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def __makeremove(self, key):
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def remove(o, selfref=ref(self), key=key):
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self = selfref()
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if self is not None:
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del self.data[key]
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return remove
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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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return WeakKeyedItemIterator(self)
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def iterkeys(self):
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return WeakKeyedKeyIterator(self)
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__iter__ = 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):
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return self.data.setdefault(ref(key, self._remove),default)
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def update(self, dict):
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d = self.data
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for key, value in dict.items():
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d[ref(key, self._remove)] = value
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class BaseIter:
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def __iter__(self):
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return self
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class WeakKeyedKeyIterator(BaseIter):
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def __init__(self, weakdict):
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self._next = weakdict.data.iterkeys().next
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def next(self):
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while 1:
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wr = self._next()
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obj = wr()
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if obj is not None:
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return obj
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class WeakKeyedItemIterator(BaseIter):
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def __init__(self, weakdict):
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self._next = weakdict.data.iteritems().next
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def next(self):
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while 1:
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wr, value = self._next()
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key = wr()
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if key is not None:
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return key, value
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class WeakValuedValueIterator(BaseIter):
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def __init__(self, weakdict):
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self._next = weakdict.data.itervalues().next
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def next(self):
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while 1:
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wr = self._next()
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obj = wr()
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if obj is not None:
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return obj
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class WeakValuedItemIterator(BaseIter):
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def __init__(self, weakdict):
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self._next = weakdict.data.iteritems().next
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def next(self):
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while 1:
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key, wr = self._next()
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value = wr()
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if value is not None:
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return key, value
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# no longer needed
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del UserDict
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