sets.py 文件源码

def difference(self, other):
        """Return the difference of two sets as a new Set.

        (I.e. all elements that are in this set and not in the other.)
        """
        result = self.__class__()
        data = result._data
        try:
            otherdata = other._data
        except AttributeError:
            otherdata = Set(other)._data
        value = True
        for elt in ifilterfalse(otherdata.__contains__, self):
            data[elt] = value
        return result

    # Membership test