| 1 | """Weak reference support for Python.
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| 2 |
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| 3 | This module is an implementation of PEP 205:
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| 4 |
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| 5 | http://www.python.org/dev/peps/pep-0205/
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| 6 | """
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| 7 |
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| 8 | # Naming convention: Variables named "wr" are weak reference objects;
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| 9 | # they are called this instead of "ref" to avoid name collisions with
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| 10 | # the module-global ref() function imported from _weakref.
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| 11 |
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| 12 | import UserDict
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| 13 |
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| 14 | from _weakref import (
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| 15 | getweakrefcount,
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| 16 | getweakrefs,
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| 17 | ref,
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| 18 | proxy,
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| 19 | CallableProxyType,
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| 20 | ProxyType,
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| 21 | ReferenceType)
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| 22 |
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| 23 | from _weakrefset import WeakSet, _IterationGuard
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| 24 |
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| 25 | from exceptions import ReferenceError
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| 26 |
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| 27 |
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| 28 | ProxyTypes = (ProxyType, CallableProxyType)
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| 29 |
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| 30 | __all__ = ["ref", "proxy", "getweakrefcount", "getweakrefs",
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| 31 | "WeakKeyDictionary", "ReferenceError", "ReferenceType", "ProxyType",
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| 32 | "CallableProxyType", "ProxyTypes", "WeakValueDictionary", 'WeakSet']
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| 33 |
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| 34 |
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| 35 | class WeakValueDictionary(UserDict.UserDict):
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| 36 | """Mapping class that references values weakly.
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| 37 |
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| 38 | Entries in the dictionary will be discarded when no strong
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| 39 | reference to the value exists anymore
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| 40 | """
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| 41 | # We inherit the constructor without worrying about the input
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| 42 | # dictionary; since it uses our .update() method, we get the right
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| 43 | # checks (if the other dictionary is a WeakValueDictionary,
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| 44 | # objects are unwrapped on the way out, and we always wrap on the
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| 45 | # way in).
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| 46 |
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| 47 | def __init__(*args, **kw):
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| 48 | if not args:
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| 49 | raise TypeError("descriptor '__init__' of 'WeakValueDictionary' "
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| 50 | "object needs an argument")
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| 51 | self = args[0]
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| 52 | args = args[1:]
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| 53 | if len(args) > 1:
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| 54 | raise TypeError('expected at most 1 arguments, got %d' % len(args))
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| 55 | def remove(wr, selfref=ref(self)):
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| 56 | self = selfref()
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| 57 | if self is not None:
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| 58 | if self._iterating:
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| 59 | self._pending_removals.append(wr.key)
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| 60 | else:
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| 61 | del self.data[wr.key]
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| 62 | self._remove = remove
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| 63 | # A list of keys to be removed
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| 64 | self._pending_removals = []
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| 65 | self._iterating = set()
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| 66 | UserDict.UserDict.__init__(self, *args, **kw)
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| 67 |
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| 68 | def _commit_removals(self):
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| 69 | l = self._pending_removals
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| 70 | d = self.data
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| 71 | # We shouldn't encounter any KeyError, because this method should
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| 72 | # always be called *before* mutating the dict.
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| 73 | while l:
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| 74 | del d[l.pop()]
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| 75 |
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| 76 | def __getitem__(self, key):
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| 77 | o = self.data[key]()
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| 78 | if o is None:
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| 79 | raise KeyError, key
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| 80 | else:
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| 81 | return o
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| 82 |
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| 83 | def __delitem__(self, key):
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| 84 | if self._pending_removals:
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| 85 | self._commit_removals()
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| 86 | del self.data[key]
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| 87 |
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| 88 | def __contains__(self, key):
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| 89 | try:
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| 90 | o = self.data[key]()
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| 91 | except KeyError:
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| 92 | return False
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| 93 | return o is not None
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| 94 |
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| 95 | def has_key(self, key):
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| 96 | try:
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| 97 | o = self.data[key]()
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| 98 | except KeyError:
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| 99 | return False
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| 100 | return o is not None
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| 101 |
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| 102 | def __repr__(self):
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| 103 | return "<WeakValueDictionary at %s>" % id(self)
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| 104 |
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| 105 | def __setitem__(self, key, value):
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| 106 | if self._pending_removals:
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| 107 | self._commit_removals()
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| 108 | self.data[key] = KeyedRef(value, self._remove, key)
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| 109 |
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| 110 | def clear(self):
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| 111 | if self._pending_removals:
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| 112 | self._commit_removals()
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| 113 | self.data.clear()
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| 114 |
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| 115 | def copy(self):
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| 116 | new = WeakValueDictionary()
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| 117 | for key, wr in self.data.items():
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| 118 | o = wr()
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| 119 | if o is not None:
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| 120 | new[key] = o
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| 121 | return new
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| 122 |
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| 123 | __copy__ = copy
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| 124 |
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| 125 | def __deepcopy__(self, memo):
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| 126 | from copy import deepcopy
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| 127 | new = self.__class__()
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| 128 | for key, wr in self.data.items():
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| 129 | o = wr()
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| 130 | if o is not None:
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| 131 | new[deepcopy(key, memo)] = o
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| 132 | return new
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| 133 |
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| 134 | def get(self, key, default=None):
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| 135 | try:
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| 136 | wr = self.data[key]
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| 137 | except KeyError:
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| 138 | return default
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| 139 | else:
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| 140 | o = wr()
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| 141 | if o is None:
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| 142 | # This should only happen
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| 143 | return default
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| 144 | else:
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| 145 | return o
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| 146 |
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| 147 | def items(self):
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| 148 | L = []
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| 149 | for key, wr in self.data.items():
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| 150 | o = wr()
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| 151 | if o is not None:
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| 152 | L.append((key, o))
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| 153 | return L
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| 154 |
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| 155 | def iteritems(self):
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| 156 | with _IterationGuard(self):
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| 157 | for wr in self.data.itervalues():
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| 158 | value = wr()
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| 159 | if value is not None:
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| 160 | yield wr.key, value
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| 161 |
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| 162 | def iterkeys(self):
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| 163 | with _IterationGuard(self):
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| 164 | for k in self.data.iterkeys():
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| 165 | yield k
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| 166 |
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| 167 | __iter__ = iterkeys
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| 168 |
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| 169 | def itervaluerefs(self):
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| 170 | """Return an iterator that yields the weak references to the values.
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| 171 |
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| 172 | The references are not guaranteed to be 'live' at the time
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| 173 | they are used, so the result of calling the references needs
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| 174 | to be checked before being used. This can be used to avoid
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| 175 | creating references that will cause the garbage collector to
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| 176 | keep the values around longer than needed.
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| 177 |
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| 178 | """
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| 179 | with _IterationGuard(self):
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| 180 | for wr in self.data.itervalues():
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| 181 | yield wr
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| 182 |
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| 183 | def itervalues(self):
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| 184 | with _IterationGuard(self):
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| 185 | for wr in self.data.itervalues():
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| 186 | obj = wr()
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| 187 | if obj is not None:
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| 188 | yield obj
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| 189 |
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| 190 | def popitem(self):
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| 191 | if self._pending_removals:
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| 192 | self._commit_removals()
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| 193 | while 1:
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| 194 | key, wr = self.data.popitem()
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| 195 | o = wr()
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| 196 | if o is not None:
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| 197 | return key, o
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| 198 |
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| 199 | def pop(self, key, *args):
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| 200 | if self._pending_removals:
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| 201 | self._commit_removals()
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| 202 | try:
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| 203 | o = self.data.pop(key)()
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| 204 | except KeyError:
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| 205 | if args:
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| 206 | return args[0]
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| 207 | raise
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| 208 | if o is None:
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| 209 | raise KeyError, key
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| 210 | else:
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| 211 | return o
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| 212 |
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| 213 | def setdefault(self, key, default=None):
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| 214 | try:
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| 215 | wr = self.data[key]
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| 216 | except KeyError:
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| 217 | if self._pending_removals:
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| 218 | self._commit_removals()
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| 219 | self.data[key] = KeyedRef(default, self._remove, key)
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| 220 | return default
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| 221 | else:
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| 222 | return wr()
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| 223 |
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| 224 | def update(*args, **kwargs):
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| 225 | if not args:
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| 226 | raise TypeError("descriptor 'update' of 'WeakValueDictionary' "
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| 227 | "object needs an argument")
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| 228 | self = args[0]
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| 229 | args = args[1:]
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| 230 | if len(args) > 1:
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| 231 | raise TypeError('expected at most 1 arguments, got %d' % len(args))
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| 232 | dict = args[0] if args else None
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| 233 | if self._pending_removals:
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| 234 | self._commit_removals()
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| 235 | d = self.data
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| 236 | if dict is not None:
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| 237 | if not hasattr(dict, "items"):
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| 238 | dict = type({})(dict)
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| 239 | for key, o in dict.items():
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| 240 | d[key] = KeyedRef(o, self._remove, key)
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| 241 | if len(kwargs):
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| 242 | self.update(kwargs)
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| 243 |
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| 244 | def valuerefs(self):
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| 245 | """Return a list of weak references to the values.
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| 246 |
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| 247 | The references are not guaranteed to be 'live' at the time
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| 248 | they are used, so the result of calling the references needs
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| 249 | to be checked before being used. This can be used to avoid
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| 250 | creating references that will cause the garbage collector to
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| 251 | keep the values around longer than needed.
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| 252 |
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| 253 | """
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| 254 | return self.data.values()
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| 255 |
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| 256 | def values(self):
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| 257 | L = []
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| 258 | for wr in self.data.values():
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| 259 | o = wr()
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| 260 | if o is not None:
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| 261 | L.append(o)
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| 262 | return L
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| 263 |
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| 264 |
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| 265 | class KeyedRef(ref):
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| 266 | """Specialized reference that includes a key corresponding to the value.
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| 267 |
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| 268 | This is used in the WeakValueDictionary to avoid having to create
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| 269 | a function object for each key stored in the mapping. A shared
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| 270 | callback object can use the 'key' attribute of a KeyedRef instead
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| 271 | of getting a reference to the key from an enclosing scope.
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| 272 |
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| 273 | """
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| 274 |
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| 275 | __slots__ = "key",
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| 276 |
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| 277 | def __new__(type, ob, callback, key):
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| 278 | self = ref.__new__(type, ob, callback)
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| 279 | self.key = key
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| 280 | return self
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| 281 |
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| 282 | def __init__(self, ob, callback, key):
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| 283 | super(KeyedRef, self).__init__(ob, callback)
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| 284 |
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| 285 |
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| 286 | class WeakKeyDictionary(UserDict.UserDict):
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| 287 | """ Mapping class that references keys weakly.
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| 288 |
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| 289 | Entries in the dictionary will be discarded when there is no
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| 290 | longer a strong reference to the key. This can be used to
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| 291 | associate additional data with an object owned by other parts of
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| 292 | an application without adding attributes to those objects. This
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| 293 | can be especially useful with objects that override attribute
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| 294 | accesses.
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| 295 | """
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| 296 |
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| 297 | def __init__(self, dict=None):
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| 298 | self.data = {}
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| 299 | def remove(k, selfref=ref(self)):
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| 300 | self = selfref()
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| 301 | if self is not None:
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| 302 | if self._iterating:
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| 303 | self._pending_removals.append(k)
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| 304 | else:
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| 305 | del self.data[k]
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| 306 | self._remove = remove
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| 307 | # A list of dead weakrefs (keys to be removed)
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| 308 | self._pending_removals = []
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| 309 | self._iterating = set()
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| 310 | if dict is not None:
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| 311 | self.update(dict)
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| 312 |
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| 313 | def _commit_removals(self):
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| 314 | # NOTE: We don't need to call this method before mutating the dict,
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| 315 | # because a dead weakref never compares equal to a live weakref,
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| 316 | # even if they happened to refer to equal objects.
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| 317 | # However, it means keys may already have been removed.
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| 318 | l = self._pending_removals
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| 319 | d = self.data
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| 320 | while l:
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| 321 | try:
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| 322 | del d[l.pop()]
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| 323 | except KeyError:
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| 324 | pass
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| 325 |
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| 326 | def __delitem__(self, key):
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| 327 | del self.data[ref(key)]
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| 328 |
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| 329 | def __getitem__(self, key):
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| 330 | return self.data[ref(key)]
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| 331 |
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| 332 | def __repr__(self):
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| 333 | return "<WeakKeyDictionary at %s>" % id(self)
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| 334 |
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| 335 | def __setitem__(self, key, value):
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| 336 | self.data[ref(key, self._remove)] = value
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| 337 |
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| 338 | def copy(self):
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| 339 | new = WeakKeyDictionary()
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| 340 | for key, value in self.data.items():
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| 341 | o = key()
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| 342 | if o is not None:
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| 343 | new[o] = value
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| 344 | return new
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| 345 |
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| 346 | __copy__ = copy
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| 347 |
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| 348 | def __deepcopy__(self, memo):
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| 349 | from copy import deepcopy
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| 350 | new = self.__class__()
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| 351 | for key, value in self.data.items():
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| 352 | o = key()
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| 353 | if o is not None:
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| 354 | new[o] = deepcopy(value, memo)
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| 355 | return new
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| 356 |
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| 357 | def get(self, key, default=None):
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| 358 | return self.data.get(ref(key),default)
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| 359 |
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| 360 | def has_key(self, key):
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| 361 | try:
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| 362 | wr = ref(key)
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| 363 | except TypeError:
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| 364 | return 0
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| 365 | return wr in self.data
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| 366 |
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| 367 | def __contains__(self, key):
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| 368 | try:
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| 369 | wr = ref(key)
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| 370 | except TypeError:
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| 371 | return 0
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| 372 | return wr in self.data
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| 373 |
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| 374 | def items(self):
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| 375 | L = []
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| 376 | for key, value in self.data.items():
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| 377 | o = key()
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| 378 | if o is not None:
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| 379 | L.append((o, value))
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| 380 | return L
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| 381 |
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| 382 | def iteritems(self):
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| 383 | with _IterationGuard(self):
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| 384 | for wr, value in self.data.iteritems():
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| 385 | key = wr()
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| 386 | if key is not None:
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| 387 | yield key, value
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| 388 |
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| 389 | def iterkeyrefs(self):
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| 390 | """Return an iterator that yields the weak references to the keys.
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| 391 |
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| 392 | The references are not guaranteed to be 'live' at the time
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| 393 | they are used, so the result of calling the references needs
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| 394 | to be checked before being used. This can be used to avoid
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| 395 | creating references that will cause the garbage collector to
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| 396 | keep the keys around longer than needed.
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| 397 |
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| 398 | """
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| 399 | with _IterationGuard(self):
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| 400 | for wr in self.data.iterkeys():
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| 401 | yield wr
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| 402 |
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| 403 | def iterkeys(self):
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| 404 | with _IterationGuard(self):
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| 405 | for wr in self.data.iterkeys():
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| 406 | obj = wr()
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| 407 | if obj is not None:
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| 408 | yield obj
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| 409 |
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| 410 | __iter__ = iterkeys
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| 411 |
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| 412 | def itervalues(self):
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| 413 | with _IterationGuard(self):
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| 414 | for value in self.data.itervalues():
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| 415 | yield value
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| 416 |
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| 417 | def keyrefs(self):
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| 418 | """Return a list of weak references to the keys.
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| 419 |
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| 420 | The references are not guaranteed to be 'live' at the time
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| 421 | they are used, so the result of calling the references needs
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| 422 | to be checked before being used. This can be used to avoid
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| 423 | creating references that will cause the garbage collector to
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| 424 | keep the keys around longer than needed.
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| 425 |
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| 426 | """
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| 427 | return self.data.keys()
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| 428 |
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| 429 | def keys(self):
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| 430 | L = []
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| 431 | for wr in self.data.keys():
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| 432 | o = wr()
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| 433 | if o is not None:
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| 434 | L.append(o)
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| 435 | return L
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| 436 |
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| 437 | def popitem(self):
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| 438 | while 1:
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| 439 | key, value = self.data.popitem()
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| 440 | o = key()
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| 441 | if o is not None:
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| 442 | return o, value
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| 443 |
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| 444 | def pop(self, key, *args):
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| 445 | return self.data.pop(ref(key), *args)
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| 446 |
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| 447 | def setdefault(self, key, default=None):
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| 448 | return self.data.setdefault(ref(key, self._remove),default)
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| 449 |
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| 450 | def update(self, dict=None, **kwargs):
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| 451 | d = self.data
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| 452 | if dict is not None:
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| 453 | if not hasattr(dict, "items"):
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| 454 | dict = type({})(dict)
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| 455 | for key, value in dict.items():
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| 456 | d[ref(key, self._remove)] = value
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| 457 | if len(kwargs):
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| 458 | self.update(kwargs)
|