1 # Access WeakSet through the weakref module. 2 # This code is separated-out because it is needed 3 # by abc.py to load everything else at startup. 4 5 from _weakref import ref 6 7 __all__ = ['WeakSet'] 8 9 10 class _IterationGuard(object): 11 # This context manager registers itself in the current iterators of the 12 # weak container, such as to delay all removals until the context manager 13 # exits. 14 # This technique should be relatively thread-safe (since sets are). 15 16 def __init__(self, weakcontainer): 17 # Don't create cycles 18 self.weakcontainer = ref(weakcontainer) 19 20 def __enter__(self): 21 w = self.weakcontainer() 22 if w is not None: 23 w._iterating.add(self) 24 return self 25 26 def __exit__(self, e, t, b): 27 w = self.weakcontainer() 28 if w is not None: 29 s = w._iterating 30 s.remove(self) 31 if not s: 32 w._commit_removals() 33 34 35 class WeakSet(object): 36 def __init__(self, data=None): 37 self.data = set() 38 def _remove(item, selfref=ref(self)): 39 self = selfref() 40 if self is not None: 41 if self._iterating: 42 self._pending_removals.append(item) 43 else: 44 self.data.discard(item) 45 self._remove = _remove 46 # A list of keys to be removed 47 self._pending_removals = [] 48 self._iterating = set() 49 if data is not None: 50 self.update(data) 51 52 def _commit_removals(self): 53 l = self._pending_removals 54 discard = self.data.discard 55 while l: 56 discard(l.pop()) 57 58 def __iter__(self): 59 with _IterationGuard(self): 60 for itemref in self.data: 61 item = itemref() 62 if item is not None: 63 yield item 64 65 def __len__(self): 66 return sum(x() is not None for x in self.data) 67 68 def __contains__(self, item): 69 try: 70 wr = ref(item) 71 except TypeError: 72 return False 73 return wr in self.data 74 75 def __reduce__(self): 76 return (self.__class__, (list(self),), 77 getattr(self, '__dict__', None)) 78 79 __hash__ = None 80 81 def add(self, item): 82 if self._pending_removals: 83 self._commit_removals() 84 self.data.add(ref(item, self._remove)) 85 86 def clear(self): 87 if self._pending_removals: 88 self._commit_removals() 89 self.data.clear() 90 91 def copy(self): 92 return self.__class__(self) 93 94 def pop(self): 95 if self._pending_removals: 96 self._commit_removals() 97 while True: 98 try: 99 itemref = self.data.pop() 100 except KeyError: 101 raise KeyError('pop from empty WeakSet') 102 item = itemref() 103 if item is not None: 104 return item 105 106 def remove(self, item): 107 if self._pending_removals: 108 self._commit_removals() 109 self.data.remove(ref(item)) 110 111 def discard(self, item): 112 if self._pending_removals: 113 self._commit_removals() 114 self.data.discard(ref(item)) 115 116 def update(self, other): 117 if self._pending_removals: 118 self._commit_removals() 119 if isinstance(other, self.__class__): 120 self.data.update(other.data) 121 else: 122 for element in other: 123 self.add(element) 124 125 def __ior__(self, other): 126 self.update(other) 127 return self 128 129 # Helper functions for simple delegating methods. 130 def _apply(self, other, method): 131 if not isinstance(other, self.__class__): 132 other = self.__class__(other) 133 newdata = method(other.data) 134 newset = self.__class__() 135 newset.data = newdata 136 return newset 137 138 def difference(self, other): 139 return self._apply(other, self.data.difference) 140 __sub__ = difference 141 142 def difference_update(self, other): 143 if self._pending_removals: 144 self._commit_removals() 145 if self is other: 146 self.data.clear() 147 else: 148 self.data.difference_update(ref(item) for item in other) 149 def __isub__(self, other): 150 if self._pending_removals: 151 self._commit_removals() 152 if self is other: 153 self.data.clear() 154 else: 155 self.data.difference_update(ref(item) for item in other) 156 return self 157 158 def intersection(self, other): 159 return self._apply(other, self.data.intersection) 160 __and__ = intersection 161 162 def intersection_update(self, other): 163 if self._pending_removals: 164 self._commit_removals() 165 self.data.intersection_update(ref(item) for item in other) 166 def __iand__(self, other): 167 if self._pending_removals: 168 self._commit_removals() 169 self.data.intersection_update(ref(item) for item in other) 170 return self 171 172 def issubset(self, other): 173 return self.data.issubset(ref(item) for item in other) 174 __lt__ = issubset 175 176 def __le__(self, other): 177 return self.data <= set(ref(item) for item in other) 178 179 def issuperset(self, other): 180 return self.data.issuperset(ref(item) for item in other) 181 __gt__ = issuperset 182 183 def __ge__(self, other): 184 return self.data >= set(ref(item) for item in other) 185 186 def __eq__(self, other): 187 if not isinstance(other, self.__class__): 188 return NotImplemented 189 return self.data == set(ref(item) for item in other) 190 191 def symmetric_difference(self, other): 192 return self._apply(other, self.data.symmetric_difference) 193 __xor__ = symmetric_difference 194 195 def symmetric_difference_update(self, other): 196 if self._pending_removals: 197 self._commit_removals() 198 if self is other: 199 self.data.clear() 200 else: 201 self.data.symmetric_difference_update(ref(item) for item in other) 202 def __ixor__(self, other): 203 if self._pending_removals: 204 self._commit_removals() 205 if self is other: 206 self.data.clear() 207 else: 208 self.data.symmetric_difference_update(ref(item) for item in other) 209 return self 210 211 def union(self, other): 212 return self._apply(other, self.data.union) 213 __or__ = union 214 215 def isdisjoint(self, other): 216 return len(self.intersection(other)) == 0 217
