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 # Caveat: the iterator will keep a strong reference to 64 # `item` until it is resumed or closed. 65 yield item 66 67 def __len__(self): 68 return len(self.data) - len(self._pending_removals) 69 70 def __contains__(self, item): 71 try: 72 wr = ref(item) 73 except TypeError: 74 return False 75 return wr in self.data 76 77 def __reduce__(self): 78 return (self.__class__, (list(self),), 79 getattr(self, '__dict__', None)) 80 81 __hash__ = None 82 83 def add(self, item): 84 if self._pending_removals: 85 self._commit_removals() 86 self.data.add(ref(item, self._remove)) 87 88 def clear(self): 89 if self._pending_removals: 90 self._commit_removals() 91 self.data.clear() 92 93 def copy(self): 94 return self.__class__(self) 95 96 def pop(self): 97 if self._pending_removals: 98 self._commit_removals() 99 while True: 100 try: 101 itemref = self.data.pop() 102 except KeyError: 103 raise KeyError('pop from empty WeakSet') 104 item = itemref() 105 if item is not None: 106 return item 107 108 def remove(self, item): 109 if self._pending_removals: 110 self._commit_removals() 111 self.data.remove(ref(item)) 112 113 def discard(self, item): 114 if self._pending_removals: 115 self._commit_removals() 116 self.data.discard(ref(item)) 117 118 def update(self, other): 119 if self._pending_removals: 120 self._commit_removals() 121 for element in other: 122 self.add(element) 123 124 def __ior__(self, other): 125 self.update(other) 126 return self 127 128 def difference(self, other): 129 newset = self.copy() 130 newset.difference_update(other) 131 return newset 132 __sub__ = difference 133 134 def difference_update(self, other): 135 self.__isub__(other) 136 def __isub__(self, other): 137 if self._pending_removals: 138 self._commit_removals() 139 if self is other: 140 self.data.clear() 141 else: 142 self.data.difference_update(ref(item) for item in other) 143 return self 144 145 def intersection(self, other): 146 return self.__class__(item for item in other if item in self) 147 __and__ = intersection 148 149 def intersection_update(self, other): 150 self.__iand__(other) 151 def __iand__(self, other): 152 if self._pending_removals: 153 self._commit_removals() 154 self.data.intersection_update(ref(item) for item in other) 155 return self 156 157 def issubset(self, other): 158 return self.data.issubset(ref(item) for item in other) 159 __le__ = issubset 160 161 def __lt__(self, other): 162 return self.data < set(ref(item) for item in other) 163 164 def issuperset(self, other): 165 return self.data.issuperset(ref(item) for item in other) 166 __ge__ = issuperset 167 168 def __gt__(self, other): 169 return self.data > set(ref(item) for item in other) 170 171 def __eq__(self, other): 172 if not isinstance(other, self.__class__): 173 return NotImplemented 174 return self.data == set(ref(item) for item in other) 175 176 def __ne__(self, other): 177 opposite = self.__eq__(other) 178 if opposite is NotImplemented: 179 return NotImplemented 180 return not opposite 181 182 def symmetric_difference(self, other): 183 newset = self.copy() 184 newset.symmetric_difference_update(other) 185 return newset 186 __xor__ = symmetric_difference 187 188 def symmetric_difference_update(self, other): 189 self.__ixor__(other) 190 def __ixor__(self, other): 191 if self._pending_removals: 192 self._commit_removals() 193 if self is other: 194 self.data.clear() 195 else: 196 self.data.symmetric_difference_update(ref(item, self._remove) for item in other) 197 return self 198 199 def union(self, other): 200 return self.__class__(e for s in (self, other) for e in s) 201 __or__ = union 202 203 def isdisjoint(self, other): 204 return len(self.intersection(other)) == 0 205
