按第二个值，reverse = True，然后按键，reverse = False，对元组列表进行排序 [英] Sort a list of tuples by second value, reverse=True and then by key, reverse=False

问题描述

我需要首先对字典进行排序，将值与reverse=True进行排序，对于重复值，需要对键进行排序，reverse=False

到目前为止，我有这个

dict = [('B', 3), ('A', 2), ('A', 1), ('I', 1), ('J', 1)]
sorted(dict.items(), key=lambda x: (x[1],x[1]), reverse=True)

返回...

[('B', 3), ('A', 2), ('J', 1), ('I', 1), ('A', 1)]

但我需要这样:

[('B', 3), ('A', 2), ('A', 1), ('I', 1), ('J', 1)]

如您所见，

当值相等时，我只能按照指定的降序对键进行排序...但是如何使它们以升序的方式进行排序?

解决方案

以下内容适用于您的输入:

d = [('B', 3), ('A', 2), ('A', 1), ('I', 1), ('J', 1)]
sorted(d,key=lambda x:(-x[1],x[0]))

由于值"是数字，因此您可以通过更改符号来轻松地反转排序顺序.

换句话说，这种排序按值(-x[1])进行排序(负号先放置大数字)，然后对相同的数字按键(x[0])进行排序. /p>

如果不能轻易地否定"您的值以将大项目放在首位，那么一个简单的解决方法是将两次排序:

from operator import itemgetter
d.sort(key=itemgetter(0))
d.sort(key=itemgetter(1),reverse=True)

之所以有效，是因为python的排序是稳定的.

I need to sort a dictionary by first, values with reverse=True, and for repeating values, sort by keys, reverse=False

So far, I have this

dict = [('B', 3), ('A', 2), ('A', 1), ('I', 1), ('J', 1)]
sorted(dict.items(), key=lambda x: (x[1],x[1]), reverse=True)

which returns...

[('B', 3), ('A', 2), ('J', 1), ('I', 1), ('A', 1)]

but I need it to be:

[('B', 3), ('A', 2), ('A', 1), ('I', 1), ('J', 1)]

as you can see, when values are equal, I can only sort the key in a decreasing fashion as specified... But how can I get them to sort in an increasing fashion?

解决方案

The following works with your input:

d = [('B', 3), ('A', 2), ('A', 1), ('I', 1), ('J', 1)]
sorted(d,key=lambda x:(-x[1],x[0]))

Since your "values" are numeric, you can easily reverse the sort order by changing the sign.

In other words, this sort puts things in order by value (-x[1]) (the negative sign puts big numbers first) and then for numbers which are the same, it orders according to key (x[0]).

If your values can't so easily be "negated" to put big items first, an easy work-around is to sort twice:

from operator import itemgetter
d.sort(key=itemgetter(0))
d.sort(key=itemgetter(1),reverse=True)

which works because python's sorting is stable.

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