这是怎么回事?

tgctg2020

>>> n=list(range(10))
>>> n
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> i=enumerate(n)
>>> list(i)
[(0, 0), (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), (8, 8), (9, 9)]
>>> reversed(list(i))
<list_reverseiterator object at 0x000001ED5850E248>
>>> list(reversed(list(1)))
Traceback (most recent call last):
  File "<pyshell#5>", line 1, in <module>
    list(reversed(list(1)))
TypeError: 'int' object is not iterable
>>> list(i)
[]
>>>


为什么list(reversed(list(1)))会报错?为什么list(i)的值会变成[]???

小伤口

enumerate()遍历数据，同时输出数据与索引
类似于for循环，只是遍历
遍历一次之后自然为空

1. >>> n=list(range(10))
   
2. >>> n
   
3. [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
   
4. >>> i=enumerate(n)
   
5. >>> list(i)
   
6. [(0, 0), (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), (8, 8), (9, 9)]
   
7. >>> list(i)
   
8. []
   
9. >>> for i in range(5):
   
10.         print(i)
    
11. 
    
12.        
    
13. 0
    
14. 1
    
15. 2
    
16. 3
    
17. 4
    
18. >>> print(i)
    
19. 4
    
20. >>>

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而你报错的原因是list(reversed(list(1)))
里面是i不是1

1. list(reversed(list(i)))
   
2. [(9, 9), (8, 8), (7, 7), (6, 6), (5, 5), (4, 4), (3, 3), (2, 2), (1, 1), (0, 0)]

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要想保存数据应该提前赋值

1. >>> i=enumerate(n)
   
2. >>> a=list(i)
   
3. >>> a
   
4. [(0, 0), (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), (8, 8), (9, 9)]
   
5. >>> a
   
6. [(0, 0), (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), (6, 6), (7, 7), (8, 8), (9, 9)]
   
7. >>>

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jackz007

        这一句写错了吧

1. ist(reversed(list(1)))

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        应该是下面这样才对

1. list(reversed(list(i)))

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