[已解决]报错：ArithmeticSequence instance has no attribute '__getitem__'？？

yuanyangxin

python基础教程上的例题（py2.0）,我输入到pycharm上却报错了，求大神帮忙看一下？

1. def checkIndex(key):
   
2.     if not isinstance(key,(int,long)):raise TypeError
   
3.     if key<0:raise IndexError
   
4. 
   
5. class ArithmeticSequence:
   
6.     def __init__(self,start=0,step=1):
   
7.         self.start=start
   
8.         self.step=step
   
9.         self.changed={}
   
10. 
    
11. def __getitem__(self,key):
    
12.     checkIndex(key)
    
13.     try:return self.changed[key]
    
14.     except KeyError:
    
15.         return self.start+key*self.step
    
16. 
    
17. def __setitem__(self,key,value):
    
18.     checkIndex(key)
    
19.     self.changed[key]=value
    
20. 
    
21. s=ArithmeticSequence(1,2)
    
22. print s[4]
    
23. s[4]=2
    
24. print s[4]
    
25. print s[5]
    

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打在pycharm里的，所以在s[4]前面加了print 让其显示输入结果

结果报错了：

1. Traceback (most recent call last):
   
2.   File "/Users/Yuan_YangXin/PycharmProjects/magicMethod/9.2/IndexError144.py", line 22, in <module>
   
3.     print s[4]
   
4. AttributeError: ArithmeticSequence instance has no attribute '__getitem__'
   
5. 
   
6. Process finished with exit code 1

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最佳答案

月排行榜 / 总排行榜

shinemic

2017-8-10 21:34:03

注意缩进。

1. def checkIndex(key):
   
2.     if not isinstance(key,(int,long)):raise TypeError
   
3.     if key<0:raise IndexError
   
4. 
   
5. class ArithmeticSequence:
   
6.     def __init__(self,start=0,step=1):
   
7.         self.start=start
   
8.         self.step=step
   
9.         self.changed={}
   
10. 
    
11.     def __getitem__(self,key):
    
12.         checkIndex(key)
    
13.         try:return self.changed[key]
    
14.         except KeyError:
    
15.             return self.start+key*self.step
    
16. 
    
17.     def __setitem__(self,key,value):
    
18.         checkIndex(key)
    
19.         self.changed[key]=value
    
20. 
    
21. s=ArithmeticSequence(1,2)
    
22. print s[4]
    
23. s[4]=2
    
24. print s[4]
    
25. print s[5]

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跳转到最佳答案楼层

shinemic

注意缩进。

1. def checkIndex(key):
   
2.     if not isinstance(key,(int,long)):raise TypeError
   
3.     if key<0:raise IndexError
   
4. 
   
5. class ArithmeticSequence:
   
6.     def __init__(self,start=0,step=1):
   
7.         self.start=start
   
8.         self.step=step
   
9.         self.changed={}
   
10. 
    
11.     def __getitem__(self,key):
    
12.         checkIndex(key)
    
13.         try:return self.changed[key]
    
14.         except KeyError:
    
15.             return self.start+key*self.step
    
16. 
    
17.     def __setitem__(self,key,value):
    
18.         checkIndex(key)
    
19.         self.changed[key]=value
    
20. 
    
21. s=ArithmeticSequence(1,2)
    
22. print s[4]
    
23. s[4]=2
    
24. print s[4]
    
25. print s[5]

复制代码

yuanyangxin

shinemic 发表于 2017-8-10 21:34
注意缩进。

谢谢