为什么Python不会为此抛出错误? [英] Why doesn't Python throw an error for this?

问题描述

MATLAB为此抛出错误:

MATLAB throws an error for this:

>> a = [2,3,4]
>> a(3:4)

  index out of bounds

如果使用Python尝试了类似的操作，为什么它不合法?

If something similar is tried with Python, why isn't it illegal?

>>> a = [2,3,4]
>>> a[2:3]
[4]

考虑到Python中的编号从零开始，是不是python中的索引'3'超出了范围?

Isn't the Index '3' in python out of bounds, considering Numbering starts from Zero in Python?

推荐答案

切片永远不会在python中引发索引超出范围的错误.

Slicing never raise error in python for out of bound indexes..

>>> s =[1,2,3]
>>> s[-1000:1000]
[1, 2, 3]

在字符串上的 docs 中(适用于列表，元组为很好):

From the docs on string(applies to lists, tuples as well):

退化的切片索引得到了很好的处理:一个索引也是如此 大由字符串大小代替，上限小于 下限返回一个空字符串.

Degenerate slice indices are handled gracefully: an index that is too large is replaced by the string size, an upper bound smaller than the lower bound returns an empty string.

文件(列表):

从i到j的s的切片被定义为具有 索引k，这样i <= k < j.如果i或j大于len(s)，请使用 len(s).如果省略i或None，请使用0.如果省略j或None，请使用 len(s).如果i大于或等于j，则切片为空.

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.

超出范围的负片索引会被截断，但不要对单元素(非片)索引尝试这样做:

Out-of-range negative slice indices are truncated, but don’t try this for single-element (non-slice) indices:

>>> word = 'HelpA'
>>> word[-100:]
'HelpA'

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