AST to symbol representation tranformation

ast2sym.py

#! /usr/bin/env python

import token
import symbol

def ast2symbol(ast):
    if len(ast) < 2:
        if type(ast) is type(""):
            return ast
        else:
            raise "Error"

    def num2sym(n):
        if token.ISTERMINAL(n):
            return token.tok_name[n]
        else:
            return symbol.sym_name[n]
        
    num = ast[0]
    rest = ast[1:]
    return [num2sym(num)] + [ast2symbol(e) for e in rest]

if __name__ == '__main__':
    import parser
    a = parser.expr("1 + 2")
    t = a.totuple()
    print ast2symbol(t)