根据最后3个字符对文本进行排序 [英] Sort text based on last 3rd character

问题描述

我正在使用sorted()函数根据最后一个字符对文本进行排序 完美的

I am using the sorted() function to sort the text based on last character which works perfectly

def sort_by_last_letter(strings):
    def last_letter(s):
        return s[-1]
    return sorted(strings,key=last_letter)

print(sort_by_last_letter(["hello","from","last","letter","a"]))

输出

['a', 'from', 'hello', 'letter', 'last']

我的要求是根据最后3个字符进行排序.但是问题是少于3个字符的单词很少，因此应该根据下一个较低的字符进行排序(如果存在则为2个，否则为最后一个).它以pythonic方式

My requirement is to sort based on last 3rd character .But problem is few of the words are less than 3 character in that case it should be sorted based on next lower placed character (2 if present else last).Searching to do it in pythonic way

目前我正在

IndexError:字符串索引超出范围

IndexError: string index out of range

def sort_by_last_letter(strings):
    def last_letter(s):
        return s[-3]
    return sorted(strings,key=last_letter)

print(sort_by_last_letter(["hello","from","last","letter","a"]))

推荐答案

您可以使用:

return sorted(strings,key=lambda x: x[max(0,len(x)-3)])

因此，我们首先计算字符串len(x)的长度，然后从中减去3.如果字符串不是那么长，我们将因此获得一个负索引，但是通过使用max(0,..)，我们可以防止出现这种情况，因此可以使用最后一个但不包括一个或最后一个字符(如果不存在这些字符).

So thus we first calculate the length of the string len(x) and subtract 3 from it. In case the string is not that long, we will thus obtain a negative index, but by using max(0,..) we prevent that and thus take the last but one, or the last character in case these do not exist.

这将在每个字符串至少包含一个字符的情况下起作用.这将产生:

This will work given every string has at least one character. This will produce:

>>> sorted(["hello","from","last","letter","a"],key=lambda x: x[max(0,len(x)-3)])
['last', 'a', 'hello', 'from', 'letter']

如果您不在乎抢七彩(换句话说，如果可以重新排序'a'和'abc')，则可以使用更优雅的方法:

In case you do not care about tie-breakers (in other words if 'a' and 'abc' can be reordered), you can use a more elegant approach:

from operator import itemgetter

return sorted(strings,key=itemgetter(slice(-3,None)))

我们在这里所做的是生成带有最后三个字符的切片，然后比较这些子字符串.然后生成:

What we here do is generating a slice with the last three characters, and then compare these substrings. This then generates:

>>> sorted(strings,key=itemgetter(slice(-3,None)))
['a', 'last', 'hello', 'from', 'letter']

由于我们与以下内容进行了比较:

Since we compare with:

   ['a', 'last', 'hello', 'from', 'letter']
#  ['a',  'ast',   'llo',  'rom',    'ter'] (comparison key)

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