def p_partselect(self, p):
        'partselect : identifier LBRACKET expression COLON expression RBRACKET'
        p[0] = Partselect(p[1], p[3], p[5], lineno=p.lineno(1))
        p.set_lineno(0, p.lineno(1))
partselect : identifier LBRACKET expression COLON expression RBRACKET