_orderable.py

def orderable(*attributes):
    def wrap(cl):
        cl = _add_cmp(cl, attrs=attributes)
        return cl
    return wrap


def _attrs_to_tuple(obj, attrs):
    """
    Create a tuple of values of *obj*'s *attributes*.
    """
    return tuple(getattr(obj, a) for a in attrs)


def _add_cmp(cl, attrs):
    """
    Add comparison methods to *cl*.
    """

    def attrs_to_tuple(obj):
        """
        Save us some typing.
        """
        return _attrs_to_tuple(obj, attrs)

    def eq(self, other):
        """
        Automatically created by attrs.
        """
        if other.__class__ is self.__class__:
            return attrs_to_tuple(self) == attrs_to_tuple(other)
        else:
            return NotImplemented

    def ne(self, other):
        """
        Automatically created by attrs.
        """
        result = eq(self, other)
        if result is NotImplemented:
            return NotImplemented
        else:
            return not result

    def lt(self, other):
        """
        Automatically created by attrs.
        """
        if isinstance(other, self.__class__):
            return attrs_to_tuple(self) < attrs_to_tuple(other)
        else:
            return NotImplemented

    def le(self, other):
        """
        Automatically created by attrs.
        """
        if isinstance(other, self.__class__):
            return attrs_to_tuple(self) <= attrs_to_tuple(other)
        else:
            return NotImplemented

    def gt(self, other):
        """
        Automatically created by attrs.
        """
        if isinstance(other, self.__class__):
            return attrs_to_tuple(self) > attrs_to_tuple(other)
        else:
            return NotImplemented

    def ge(self, other):
        """
        Automatically created by attrs.
        """
        if isinstance(other, self.__class__):
            return attrs_to_tuple(self) >= attrs_to_tuple(other)
        else:
            return NotImplemented

    cl.__eq__ = eq
    cl.__ne__ = ne
    cl.__lt__ = lt
    cl.__le__ = le
    cl.__gt__ = gt
    cl.__ge__ = ge

    return cl