access weakset through the weakref module this code is separatedout because it is needed by abc py to load everything else at startup 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 threadsafe since sets are don t create cycles a list of keys to be removed caveat the iterator will keep a strong reference to item until it is resumed or closed access weakset through the weakref module this code is separated out because it is needed by abc py to load everything else at startup 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 don t create cycles a list of keys to be removed caveat the iterator will keep a strong reference to item until it is resumed or closed
from _weakref import ref
from types import GenericAlias

__all__ = ['WeakSet']


class _IterationGuard:
    
    
    
    

    def __init__(self, weakcontainer):
        
        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
        
        self._pending_removals = []
        self._iterating = set()
        if data is not None:
            self.update(data)

    def _commit_removals(self):
        pop = self._pending_removals.pop
        discard = self.data.discard
        while True:
            try:
                item = pop()
            except IndexError:
                return
            discard(item)

    def __iter__(self):
        with _IterationGuard(self):
            for itemref in self.data:
                item = itemref()
                if item is not None:
                    
                    
                    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),), self.__getstate__()

    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)

    __class_getitem__ = classmethod(GenericAlias)