“笨办法学python” ex49

1.创建目录结构：

首先创建文件ex49,在ex49中创建skeleton，具体文件如下：

 

2.parser.py文件中的代码(书中代码）:

 

 1 class ParserError(Exception):
 2     pass
 3     
 4 class Sentence(object):
 5     def __init__(self,subject,verb,object):
 6         self.subject=subject[1]
 7         self.verb=verb[1]
 8         self.object=object[1]
 9         
10 def peek(word_list):
11     
12     if word_list:
13         word=word_list[0]
14         return word[0]
15     else:
17         return None
18         
19 def match(word_list,expecting):
20     
21     if word_list:
22         word=word_list.pop(0)
23         if word[0]==expecting:
24             
25             return word
26         else:
27             return None
28     else:
29         return None
30 
31 def skip(word_list,word_type):
32     result=''
33     while peek(word_list)==word_type:
34         result = match(word_list,word_type)
35     return result
36         
37 def parse_verb(word_list):
38     skip(word_list,'stop')
39     
40     if peek(word_list)=='verb':
41         return match(word_list,'verb')
42     else:
43         raise ParserError("Excepted a verb next")
44         
45 def parse_object(word_list):
46     skip(word_list,'stop')
47     next=peek(word_list)
48     
49     if next=='noun':
50         return match(word_list,'noun')
51     if next=='direction':
52         return match(word_list,'direction')
53     else:
54         raise ParserError("Excepted a noun or direction next.")
55         
56 def parse_subject(word_list,subj):
57     verb=parse_verb(word_list)
58     obj=parse_object(word_list)
59     a=Sentence(subj,verb,obj)
63     return a
64     
65     
66 def parse_sentence(word_list):
67     skip(word_list,'stop')
68     start=peek(word_list)
69     if start=='noun':
70         subj=match(word_list,'noun')
71         return parse_subject(word_list,subj)
72         
73     elif start=='verb':
74         return parse_subject(word_list,('noun','player'))
75     else:
76         raise ParserError("Must start with subject,object,or verb not :%s %start")

 

 3.parse_tests.py中为对parser.py进行单元测试代码（编写代码）：

 1 from nose.tools import *
 2 import sys
 3 sys.path.append('H:\\ex49\\skeleton')
 4 import ex49.parser
 5 
 6 word_listA=[('verb','kill'),('direction','north')]
 7 def test_peek():
 8     result=ex49.parser.peek([('verb','kill'),('direction','north')])
 9     assert_equal(result,'verb')
10     
11 def test_match():
12     result=ex49.parser.match(word_listA,'verb')
13     assert_equal(result,('verb','kill'))
14     assert_equal(word_listA,[('direction','north')])
15     result1=ex49.parser.match(word_listA,'stop')
16     assert_equal(result1,None)    
17     
18 def test_skip():
19     result=ex49.parser.skip([('verb','kill'),('direction','north')],'verb')
20     assert_equal(result,('verb','kill'))
21     
22 def test_parse_verb():
23     result=ex49.parser.parse_verb([('verb','kill'),('direction','north')])
24     assert_equal(result,('verb','kill'))
25     assert_raises(ex49.parser.ParserError,ex49.parser.parse_verb,[('stop','the'),('direction','north')])
26     
27 
28 def test_parse_object():
29     result=ex49.parser.parse_object([('stop','the'),('noun','door')])
30     assert_equal(result,('noun','door'))
31     result1=ex49.parser.parse_object([('stop','the'),('direction','north')])
32     assert_equal(result1,('direction','north'))    
33     assert_raises(ex49.parser.ParserError,ex49.parser.parse_object,[('stop','the'),('verb','go')])
34 
35 def test_parse_subject():
36     result=ex49.parser.parse_subject([('verb','go'),('stop','the'),('noun','door')],('m','k'))
37     assert_equal(result.subject,'k')
38     assert_equal(result.verb,'go')
39     assert_equal(result.object,'door')
40     
41 def test_parse_sentence():
42     result=ex49.parser.parse_sentence([('verb','go'),('stop','the'),('noun','door')])
43     assert_equal(result.subject,'player')
44     assert_equal(result.verb,'go')
45     assert_equal(result.object,'door')
46     
47     result1=ex49.parser.parse_sentence([('stop','in'),('noun','door'),('verb','go'),('direction','north')])
48     assert_equal(result1.subject,'door')
49     assert_equal(result1.verb,'go')
50     assert_equal(result1.object,'north')
51     
52     assert_raises(ex49.parser.ParserError,ex49.parser.parse_sentence,[('stop','in'),('stop','the')])
53            

 

 4.遇到的问题：

1）从ex49中导入parse.py时，用from ex49 import parse出错

提示ImportError: No module named ex49

发现是同级目录导入文件方式错误，参考http://blog.chinaunix.net/uid-26000296-id-4372344.html文章中第三点

最后更改为以下导入方式才可行：

import sys
sys.path.append('H:\\ex49\\skeleton')
import ex49.parser

转载于:https://www.cnblogs.com/sunyucui/p/6691404.html