Class WeakSet

Lib/_weakrefset.py:11–147

class WeakSet:
    def __init__(self, data=None):
        self.data = set()

        def _remove(item, selfref=ref(self)):
            self = selfref()
            if self is not None:
                self.data.discard(item)

        self._remove = _remove
        if data is not None:
            self.update(data)

    def __iter__(self):
        for itemref in self.data.copy():
            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)

    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):
        self.data.add(ref(item, self._remove))

    def clear(self):
        self.data.clear()

    def copy(self):
        return self.__class__(self)

    def pop(self):
        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):
        self.data.remove(ref(item))

    def discard(self, item):
        self.data.discard(ref(item))