multiset.py 文件源码

def combine(self, *others):
        r"""Return a new multiset with all elements from the multiset and the others with their multiplicities summed up.

        >>> ms = Multiset('aab')
        >>> sorted(ms.combine('bc'))
        ['a', 'a', 'b', 'b', 'c']

        You can also use the ``+`` operator for the same effect. However, the operator version
        will only accept a set as other operator, not any iterable, to avoid errors.

        >>> ms = Multiset('aab')
        >>> sorted(ms + Multiset('a'))
        ['a', 'a', 'a', 'b']

        For a variant of the operation which modifies the multiset in place see
        :meth:`update`.

        Args:
            others: The other sets to add to the multiset. Can also be any :class:`~typing.Iterable`\[~T]
                or :class:`~typing.Mapping`\[~T, :class:`int`] which are then converted to :class:`Multiset`\[~T].

        Returns:
            The multiset resulting from the addition of the sets.
        """
        result = self.__copy__()
        _elements = result._elements
        _total = result._total
        for other in map(self._as_mapping, others):
            for element, multiplicity in other.items():
                old_multiplicity = _elements.get(element, 0)
                new_multiplicity = old_multiplicity + multiplicity
                if old_multiplicity > 0 and new_multiplicity <= 0:
                    del _elements[element]
                    _total -= old_multiplicity
                elif new_multiplicity > 0:
                    _elements[element] = new_multiplicity
                    _total += multiplicity
        result._total = _total
        return result