compatsets.py

用python实现的邮件过滤器

        try:
            return element in self._data
        except TypeError:
            transform = getattr(element, "_as_temporarily_immutable", None)
            if transform is None:
                raise # re-raise the TypeError exception we caught
            return transform() in self._data

    # Subset and superset test

    def issubset(self, other):
        """Report whether another set contains this set."""
        self._binary_sanity_check(other)
        if len(self) > len(other):  # Fast check for obvious cases
            return False
        otherdata = other._data
        for elt in self:
            if elt not in otherdata:
                return False
        return True

    def issuperset(self, other):
        """Report whether this set contains another set."""
        self._binary_sanity_check(other)
        if len(self) < len(other):  # Fast check for obvious cases
            return False
        selfdata = self._data
        for elt in other:
            if elt not in selfdata:
                return False
        return True

    # Inequality comparisons using the is-subset relation.
    __le__ = issubset
    __ge__ = issuperset

    def __lt__(self, other):
        self._binary_sanity_check(other)
        return len(self) < len(other) and self.issubset(other)

    def __gt__(self, other):
        self._binary_sanity_check(other)
        return len(self) > len(other) and self.issuperset(other)

    # Assorted helpers

    def _binary_sanity_check(self, other):
        # Check that the other argument to a binary operation is also
        # a set, raising a TypeError otherwise.
        if not isinstance(other, BaseSet):
            raise TypeError, "Binary operation only permitted between sets"

    def _compute_hash(self):
        # Calculate hash code for a set by xor'ing the hash codes of
        # the elements.  This ensures that the hash code does not depend
        # on the order in which elements are added to the set.  This is
        # not called __hash__ because a BaseSet should not be hashable;
        # only an ImmutableSet is hashable.
        result = 0
        for elt in self:
            result ^= hash(elt)
        return result

    def _update(self, iterable):
        # The main loop for update() and the subclass __init__() methods.
        data = self._data

        # Use the fast update() method when a dictionary is available.
        if isinstance(iterable, BaseSet):
            data.update(iterable._data)
            return
        if isinstance(iterable, dict):
            data.update(iterable)
            return

        value = True
        it = iter(iterable)
        while True:
            try:
                for element in it:
                    data[element] = value
                return
            except TypeError:
                transform = getattr(element, "_as_immutable", None)
                if transform is None:
                    raise # re-raise the TypeError exception we caught
                data[transform()] = value


class ImmutableSet(BaseSet):
    """Immutable set class."""

    __slots__ = ['_hashcode']

    # BaseSet + hashing

    def __init__(self, iterable=None):
        """Construct an immutable set from an optional iterable."""
        self._hashcode = None
        self._data = {}
        if iterable is not None:
            self._update(iterable)

    def __hash__(self):
        if self._hashcode is None:
            self._hashcode = self._compute_hash()
        return self._hashcode


class Set(BaseSet):
    """ Mutable set class."""

    __slots__ = []

    # BaseSet + operations requiring mutability; no hashing

    def __init__(self, iterable=None):
        """Construct a set from an optional iterable."""
        self._data = {}
        if iterable is not None:
            self._update(iterable)

    def __hash__(self):
        """A Set cannot be hashed."""
        # We inherit object.__hash__, so we must deny this explicitly
        raise TypeError, "Can't hash a Set, only an ImmutableSet."

    # In-place union, intersection, differences.
    # Subtle:  The xyz_update() functions deliberately return None,
    # as do all mutating operations on built-in container types.
    # The __xyz__ spellings have to return self, though.

    def __ior__(self, other):
        """Update a set with the union of itself and another."""
        self._binary_sanity_check(other)
        self._data.update(other._data)
        return self

    def union_update(self, other):
        """Update a set with the union of itself and another."""
        self |= other

    def __iand__(self, other):
        """Update a set with the intersection of itself and another."""
        self._binary_sanity_check(other)
        self._data = (self & other)._data
        return self

    def intersection_update(self, other):
        """Update a set with the intersection of itself and another."""
        self &= other

    def __ixor__(self, other):
        """Update a set with the symmetric difference of itself and another."""
        self._binary_sanity_check(other)
        data = self._data
        value = True
        for elt in other:
            if elt in data:
                del data[elt]
            else:
                data[elt] = value
        return self

    def symmetric_difference_update(self, other):
        """Update a set with the symmetric difference of itself and another."""
        self ^= other

    def __isub__(self, other):
        """Remove all elements of another set from this set."""
        self._binary_sanity_check(other)
        data = self._data
        for elt in other:
            if elt in data:
                del data[elt]
        return self

    def difference_update(self, other):
        """Remove all elements of another set from this set."""
        self -= other

    # Python dict-like mass mutations: update, clear

    def update(self, iterable):
        """Add all values from an iterable (such as a list or file)."""
        self._update(iterable)

    def clear(self):
        """Remove all elements from this set."""
        self._data.clear()

    # Single-element mutations: add, remove, discard

    def add(self, element):
        """Add an element to a set.

        This has no effect if the element is already present.
        """
        try:
            self._data[element] = True
        except TypeError:
            transform = getattr(element, "_as_immutable", None)
            if transform is None:
                raise # re-raise the TypeError exception we caught
            self._data[transform()] = True

    def remove(self, element):
        """Remove an element from a set; it must be a member.

        If the element is not a member, raise a KeyError.
        """
        try:
            del self._data[element]
        except TypeError:
            transform = getattr(element, "_as_temporarily_immutable", None)
            if transform is None:
                raise # re-raise the TypeError exception we caught
            del self._data[transform()]

    def discard(self, element):
        """Remove an element from a set if it is a member.

        If the element is not a member, do nothing.
        """
        try:
            self.remove(element)
        except KeyError:
            pass

    def pop(self):
        """Remove and return an arbitrary set element."""
        return self._data.popitem()[0]

    def _as_immutable(self):
        # Return a copy of self as an immutable set
        return ImmutableSet(self)

    def _as_temporarily_immutable(self):
        # Return self wrapped in a temporarily immutable set
        return _TemporarilyImmutableSet(self)


class _TemporarilyImmutableSet(BaseSet):
    # Wrap a mutable set as if it was temporarily immutable.
    # This only supplies hashing and equality comparisons.

    def __init__(self, set):
        self._set = set
        self._data = set._data  # Needed by ImmutableSet.__eq__()

    def __hash__(self):
        return self._set._compute_hash()