編譯原理----詞法分析程序----python語言版

對python的應用還是不熟練，很多實用的方法沒掌握，下面的程序本來是用C寫的，為了練習一下python，又用python改寫的，很粗糙，有bug，不過能運行出結果，嘿嘿，以后學好了python再來優化吧

 
          # 
           -*- 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  
          " 
          運算符\t 
          ",test[i] 
          
          
          continue 
          
      
          if test[i-1]  
          in Number: 
          
          
          continue 
          
      
          if test[i]  
          in Number: 
          
          
          print  
          " 
          數字\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  
          " 
          關鍵字\t 
          ",temp 
          
      
          else: 
          
          
          print  
          " 
          標識符\t 
          ",temp 
         

2012年3月21日 22:43:52改寫的代碼：

 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  " 運算符\t ",test[i]
20          continue
21      if test[i].isdigit():
22          print  " 數字\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  " 關鍵字\t ",temp
40      else:
41          print  " 標識符\t ",temp

     i-=1