def geodist(self, name, place1, place2, unit=None):
        """
        Return the distance between ``place1`` and ``place2`` members of the
        ``name`` key.
        The units must be one of the following : m, km mi, ft. By default
        meters are used.
        """
        pieces = [name, place1, place2]
        if unit and unit not in ('m', 'km', 'mi', 'ft'):
            raise DataError("GEODIST invalid unit")
        elif unit:
            pieces.append(unit)
        return self.execute_command('GEODIST', *pieces)