词法分析程序（python）完整代码

  用于编译原理作业，已经通过编译，用的是文件的输入输出形式，如果有需要可以自己改成终端输入输出形式。

class WORD(object):
    def __init__(self, typenum, word):
        self.typenum = typenum
        self.word = word


str_input = ""

rwtab = ["begin", "end", "do", "if", "then", "while"]
ch = ""
p_input = 0
p_token = 0


def getchar():
    global ch, p_input
    # print("input:%d" % p_input)
    ch = str_input[p_input]
    p_input += 1
    return ch


# 去掉空格
def delete_blank():
    global ch, p_input
    while ch == " " or ch == 10:
        ch = str_input[p_input]
        p_input += 1


def concat(str1):
  global ch
  str1 += ch
  return str1


def letter():
    if ('a' <= ch <= 'z') or ('A' <= ch <= 'Z'):
        return True
    else:
        return False


def digit():
    if '0' <= ch <= '9':
        return True
    else:
        return False


def reserve(str1):
   global rwtab
   for find_str in rwtab:
       if str1 == find_str:
           return rwtab.index(find_