奇怪的 Python 特性

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这是一个创建于 2627 天前的主题，其中的信息可能已经有所发展或是发生改变。

好吧,是一个 feature 还是 bug 已经搞不清了

Ubuntu 16.04.03 Python3.5.2

>>> a = ''
>>> a[1:-1]
''
>>> a[2:-1]
''
>>> a[3:-1]
''

13 条回复 • 2017-09-02 10:16:00 +08:00

clino

2017-09-01 14:52:03 +08:00

你觉得应该返回什么?

eloah

2017-09-01 14:54:57 +08:00

@clino
raise IndexError

013231

2017-09-01 15:12:06 +08:00

是 feature。
https://docs.python.org/3.6/library/stdtypes.html#common-sequence-operations

s[i:j:k]
“ The slice of s from i to j is defined as the sequence of items with index k such that i <= k < j. If i or j is greater than len(s), use len(s). If i is omitted or None, use 0. If j is omitted or None, use len(s). If i is greater than or equal to j, the slice is empty.”

est

2017-09-01 15:17:23 +08:00

In [457]: a='a'

In [458]: a[0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0][0]
Out[458]: 'a'

mark06

2017-09-01 15:18:25 +08:00

> However, out of range slice indexes are handled gracefully when used for slicing:

```
>>> word[4:42]
'on'
>>> word[42:]
''
```
[document]( https://docs.python.org/3.5/tutorial/introduction.html#strings)