在计算的len的时候碰到
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TypeError: object of type 'listiterator' has no len()
说明这个对象是个iterator，是没有len的，翻了下google
普遍的做法是使用len(list(iterator))
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>>> l1 = [1, 2, 3]
>>> it = iter(l1)
>>> it
<listiterator object at 0x1013089d0>
>>> type(it)
<type 'listiterator'>
>>> l2 = list(it)
>>> l2
[1, 2, 3]
>>> list(it)
[]
>>> l2
[1, 2, 3]
>>> l1
[1, 2, 3]
>>>
>>> l1 = [1, 2, 3]
>>> it = iter(l1)
>>> len(list(it))
3
>>> list(it)
[]
注意
这个terator：list(it)是不能再用的，也就是重复遍历的话只有第一次有数据的
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>>> l1 = [1, 2, 3]
>>> it = iter(l1)
>>> for i in it:
... print i
...
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2
3
>>> for i in it:
... print i
...
>>> for i in l1:
... print i
...
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2
3
>>> for i in l1:
... print i
...
1
2
3
>>>