编译原理词法分析程序python语言版

对python的应用还是不熟练，很多实用的方法没掌握，下面的程序本来是用C写的，为了练习一下python，又用python改写的，很粗糙，有bug，不过能运行出结果，嘿嘿，以后学好了python再来优化吧

# -*- coding: cp936 -*-
Keyword = ("begin","end","if","while","var","procedure","else","for","do","int","read","write")
Yunsuanfu = ('+','-','*','/','<','>','%','=')
Fenjiefu = (',',';','(',')','{','}',':')
Kongbai = (' ','\t','\n')
Number = ('0','1','2','3','4','5','6','7','8','9')

test="var a=10;\nvar b,c;\nprocedure p; \n\tbegin\n\t\tc=a+b\n\tend\n"
print test
length=len(test)

for i in range(length):
    if test[i] in Kongbai:
        continue
    if test[i] in Fenjiefu:
        print "分界符\t",test[i]
        continue
    if test[i] in Yunsuanfu:
        print "运算符\t",test[i]
        continue
    if test[i-1] in Number:
        continue
    if test[i] in Number:
        print "数字\t",
        while test[i] in Number:
            print test[i],
            i+=1
        print ''
    if test[i-1] in Number or (test[i-1]>='a' and test[i-1]<='z'):
        continue
    j=0
    temp = ""
    while True:
        if test[i] in Kongbai or test[i] in Yunsuanfu or test[i] in Fenjiefu:
            break
        else:
            j+=1
        i+=1
    temp = test[i-j:i]
    if temp in Keyword:
        print "关键字\t",temp
    else:
        print "标识符\t",temp

2012年3月21日 22:43:52改写的代码：

1 # -*- coding: cp936 -*-
2 Keyword = ("begin","end","if","while","var","procedure","else","for","do","int","read","write")
3 Yunsuanfu = ('+','-','*','/','<','>','%','=')
4 Fenjiefu = (',',';','(',')','{','}',':')
5 Kongbai = (' ','\t','\n')
6
7 test="var a=10;\nvar b,c;\nprocedure p; \n\tbegin\n\t\tc=a+b\n\tend\n"
8 print test
9 length=len(test)
10 i=-1
11 while i < length:
12     i+=1
13     if test[i] in Kongbai:
14         continue
15     if test[i] in Fenjiefu:
16         print "分界符\t",test[i]
17         continue
18     if test[i] in Yunsuanfu:
19         print "运算符\t",test[i]
20         continue
21     if test[i].isdigit():
22         print "数字\t",
23         while test[i].isdigit():
24             print test[i],
25             i+=1
26         print ''
27         i-=1
28         continue
29     j=0
30     temp = ""
31     while True:
32         if test[i] in Kongbai or test[i] in Yunsuanfu or test[i] in Fenjiefu:
33             break
34         else:
35             j+=1
36         i+=1
37     temp = test[i-j:i]
38     if temp in Keyword:
39         print "关键字\t",temp
40     else:
41         print "标识符\t",temp

42 i-=1