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: 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: 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 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 for element in other: 120 self.add(element) 121 122 def __ior__(self, other): 123 self.update(other) 124 return self 125 126 def difference(self, other): 127 newset = self.copy() 128 newset.difference_update(other) 129 return newset 130 __sub__ = difference 131 132 def difference_update(self, other): 133 self.__isub__(other) 134 def __isub__(self, other): 135 if self._pending_removals: 136 self._commit_removals() 137 if self is other: 138 self.data.clear() 139 else: 140 self.data.difference_update(ref(item) for item in other) 141 return self 142 143 def intersection(self, other): 144 return self.__class__(item for item in other if item in self) 145 __and__ = intersection 146 147 def intersection_update(self, other): 148 self.__iand__(other) 149 def __iand__(self, other): 150 if self._pending_removals: 151 self._commit_removals() 152 self.data.intersection_update(ref(item) for item in other) 153 return self 154 155 def issubset(self, other): 156 return self.data.issubset(ref(item) for item in other) 157 __le__ = issubset 158 159 def __lt__(self, other): 160 return self.data < set(ref(item) for item in other) 161 162 def issuperset(self, other): 163 return self.data.issuperset(ref(item) for item in other) 164 __ge__ = issuperset 165 166 def __gt__(self, other): 167 return self.data > set(ref(item) for item in other) 168 169 def __eq__(self, other): 170 if not isinstance(other, self.__class__): 171 return NotImplemented 172 return self.data == set(ref(item) for item in other) 173 174 def symmetric_difference(self, other): 175 newset = self.copy() 176 newset.symmetric_difference_update(other) 177 return newset 178 __xor__ = symmetric_difference 179 180 def symmetric_difference_update(self, other): 181 self.__ixor__(other) 182 def __ixor__(self, other): 183 if self._pending_removals: 184 self._commit_removals() 185 if self is other: 186 self.data.clear() 187 else: 188 self.data.symmetric_difference_update(ref(item, self._remove) for item in other) 189 return self 190 191 def union(self, other): 192 return self.__class__(e for s in (self, other) for e in s) 193 __or__ = union 194 195 def isdisjoint(self, other): 196 return len(self.intersection(other)) == 0 197
