以下のような配列を考えます ```python output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]] ``` このような配列を各二番目の要素（数値）で降順ソートするにはどうすればよいでしょうか

いくつか方法があります。 1つめ ```python >>> output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]] >>> l = [[y,x] for x,y in output] >>> l.sort(reverse=True) >>> [[x,y] for y,x in l] [['d', 0.9], ['b', 0.8], ['a', 0.7], ['c', 0.02]] ``` 2つめ ```python >>> output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]] >>> sorted(output, key=lambda x: -x[1]) [['d', 0.9], ['b', 0.8], ['a', 0.7], ['c', 0.02]] ``` 3つめ ```python >>> from operator import itemgetter >>> output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]] >>> sorted(output, key=itemgetter(1), reverse=True) [['d', 0.9], ['b', 0.8], ['a', 0.7], ['c', 0.02]] ```

pythonの二次元配列を降順ソートするには

以下のような配列を考えます

python
1output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]]

このような配列を各二番目の要素（数値）で降順ソートするにはどうすればよいでしょうか

行動規範の内容に同意します

回答1件

ベストアンサー

いくつか方法があります。

1つめ

python
1>>> output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]]
2>>> l = [[y,x] for x,y in output]
3>>> l.sort(reverse=True)
4>>> [[x,y] for y,x in l]
5[['d', 0.9], ['b', 0.8], ['a', 0.7], ['c', 0.02]]

2つめ

python
1>>> output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]]
2>>> sorted(output, key=lambda x: -x[1])
3[['d', 0.9], ['b', 0.8], ['a', 0.7], ['c', 0.02]]

3つめ

python
1>>> from operator import itemgetter
2>>> output = [["a",0.7],["b",0.8],["c",0.02],["d",0.9]]
3>>> sorted(output, key=itemgetter(1), reverse=True)
4[['d', 0.9], ['b', 0.8], ['a', 0.7], ['c', 0.02]]