sets.py 文件源码

def difference_update(self, other):
        """Remove all elements of another set from this set."""
        data = self._data
        if not isinstance(other, BaseSet):
            other = Set(other)
        if self is other:
            self.clear()
        for elt in ifilter(data.__contains__, other):
            del data[elt]

    # Python dict-like mass mutations: update, clear