在pandas DataFrame中重新排序MultiIndex的级别

Question

我有一个看起来像这样的DataFrame:

>>> df = pd.DataFrame(index=pd.MultiIndex.from_tuples([(num,letter,color) 
                    for num in range(1,3) 
                    for letter in ['a','b','c'] for color in ['Red','Green']], 
                    names=['Number','Letter','Color']))
>>> df['Value'] = np.random.randint(1,100,len(df))
>>> df
                     Value
Number Letter Color       
1      a      Red       97
              Green     61
       b      Red       97
              Green     98
       c      Red       91
              Green     47
2      a      Red       17
              Green     63
       b      Red       26
              Green     73
       c      Red       34
              Green     68

但我实际上希望我的索引被命令'Letter,Color,Number'.

我目前这样做如下:

>>> df.reset_index().set_index(['Letter','Color','Number'])
                     Value
Letter Color Number       
a      Red   1          97
       Green 1          61
b      Red   1          97
       Green 1          98
c      Red   1          91
       Green 1          47
a      Red   2          17
       Green 2          63
b      Red   2          26
       Green 2          73
c      Red   2          34
       Green 2          68

这是最好的方法吗？

Answer 1

最好用来reorder_levels操纵MultiIndex级别的顺序.只需按照您想要的顺序传递级别名称/数字列表:

>>> df.reorder_levels(['Letter','Color','Number'])
                     Value
Letter Color Number       
a      Red   1          41
       Green 1          56
b      Red   1          43
       Green 1          42
c      Red   1          89
       Green 1          18
a      Red   2          55
       Green 2          93
b      Red   2          64
       Green 2           9
c      Red   2          21
       Green 2          93

还有swaplevel,如果你只是想交换两个级别的位置.