# Access WeakSet through the weakref module. # This code is separated-out because it is needed # by abc.py to load everything else at startup. from _weakref import ref __all__ = ['WeakSet'] class _IterationGuard: # This context manager registers itself in the current iterators of the # weak container, such as to delay all removals until the context manager # exits. # This technique should be relatively thread-safe (since sets are). def __init__(self, weakcontainer): # Don't create cycles self.weakcontainer = ref(weakcontainer) def __enter__(self): w = self.weakcontainer() if w is not None: w._iterating.add(self) return self def __exit__(self, e, t, b): w = self.weakcontainer() if w is not None: s = w._iterating s.remove(self) if not s: w._commit_removals() class WeakSet: def __init__(self, data=None): self.data = set() def _remove(item, selfref=ref(self)): self = selfref() if self is not None: if self._iterating: self._pending_removals.append(item) else: self.data.discard(item) self._remove = _remove # A list of keys to be removed self._pending_removals = [] self._iterating = set() if data is not None: self.update(data) def _commit_removals(self): l = self._pending_removals discard = self.data.discard while l: discard(l.pop()) def __iter__(self): with _IterationGuard(self): for itemref in self.data: item = itemref() if item is not None: # Caveat: the iterator will keep a strong reference to # `item` until it is resumed or closed. yield item def __len__(self): return len(self.data) - len(self._pending_removals) def __contains__(self, item): try: wr = ref(item) except TypeError: return False return wr in self.data def __reduce__(self): return (self.__class__, (list(self),), getattr(self, '__dict__', None)) def add(self, item): if self._pending_removals: self._commit_removals() self.data.add(ref(item, self._remove)) def clear(self): if self._pending_removals: self._commit_removals() self.data.clear() def copy(self): return self.__class__(self) def pop(self): if self._pending_removals: self._commit_removals() while True: try: itemref = self.data.pop() except KeyError: raise KeyError('pop from empty WeakSet') from None item = itemref() if item is not None: return item def remove(self, item): if self._pending_removals: self._commit_removals() self.data.remove(ref(item)) def discard(self, item): if self._pending_removals: self._commit_removals() self.data.discard(ref(item)) def update(self, other): if self._pending_removals: self._commit_removals() for element in other: self.add(element) def __ior__(self, other): self.update(other) return self def difference(self, other): newset = self.copy() newset.difference_update(other) return newset __sub__ = difference def difference_update(self, other): self.__isub__(other) def __isub__(self, other): if self._pending_removals: self._commit_removals() if self is other: self.data.clear() else: self.data.difference_update(ref(item) for item in other) return self def intersection(self, other): return self.__class__(item for item in other if item in self) __and__ = intersection def intersection_update(self, other): self.__iand__(other) def __iand__(self, other): if self._pending_removals: self._commit_removals() self.data.intersection_update(ref(item) for item in other) return self def issubset(self, other): return self.data.issubset(ref(item) for item in other) __le__ = issubset def __lt__(self, other): return self.data < set(map(ref, other)) def issuperset(self, other): return self.data.issuperset(ref(item) for item in other) __ge__ = issuperset def __gt__(self, other): return self.data > set(map(ref, other)) def __eq__(self, other): if not isinstance(other, self.__class__): return NotImplemented return self.data == set(map(ref, other)) def symmetric_difference(self, other): newset = self.copy() newset.symmetric_difference_update(other) return newset __xor__ = symmetric_difference def symmetric_difference_update(self, other): self.__ixor__(other) def __ixor__(self, other): if self._pending_removals: self._commit_removals() if self is other: self.data.clear() else: self.data.symmetric_difference_update(ref(item, self._remove) for item in other) return self def union(self, other): return self.__class__(e for s in (self, other) for e in s) __or__ = union def isdisjoint(self, other): return len(self.intersection(other)) == 0 def __repr__(self): return repr(self.data)