Python pandas根据行中的值排序列

Question

如何根据最后一行的值对列进行排序？在下面的例子中,我的最终df将按以下顺序排列:'ddd''aaa''ppp''ffff'.

>>> df = DataFrame(np.random.randn(10, 4), columns=['ddd', 'fff', 'aaa', 'ppp'])
>>> df
        ddd       fff       aaa       ppp
0 -0.177438  0.102561 -1.318710  1.321252
1  0.980348  0.786721  0.374506 -1.411019
2  0.405112  0.514216  1.761983 -0.529482
3  1.659710 -1.017048 -0.737615 -0.388145
4 -0.472223  1.407655 -0.129119 -0.912974
5  1.221324 -0.656599  0.563152 -0.900710
6 -1.816420 -2.898094 -0.232047 -0.648904
7  2.793261  0.568760 -0.850100  0.654704
8 -2.180891  2.054178 -1.050897 -1.461458
9 -1.123756  1.245987 -0.239863  0.359759

Answer 1

[更新以简化]

TL;博士:

In [29]: new_columns = df.columns[df.ix[df.last_valid_index()].argsort()]

In [30]: df[new_columns]
Out[30]: 
        aaa       ppp       fff       ddd
0  0.328281  0.375458  1.188905  0.503059
1  0.305457  0.186163  0.077681 -0.543215
2  0.684265  0.681724  0.210636 -0.532685
3 -1.134292  1.832272  0.067946  0.250131
4 -0.834393  0.010211  0.649963 -0.551448
5 -1.032405 -0.749949  0.442398  1.274599

一些解释如下.一,建立DataFrame:

In [24]: df = pd.DataFrame(np.random.randn(6, 4), columns=['ddd', 'fff', 'aaa', 'ppp'])

In [25]: df
Out[25]: 
        ddd       fff       aaa       ppp
0  0.503059  1.188905  0.328281  0.375458
1 -0.543215  0.077681  0.305457  0.186163
2 -0.532685  0.210636  0.684265  0.681724
3  0.250131  0.067946 -1.134292  1.832272
4 -0.551448  0.649963 -0.834393  0.010211
5  1.274599  0.442398 -1.032405 -0.749949

获取最后一行:

In [26]: last_row = df.ix[df.last_valid_index()]

获取将对其进行排序的索引:

In [27]: last_row.argsort()
Out[27]: 
ddd    2
fff    3
aaa    1
ppp    0
Name: 5, Dtype: int32

用它来索引df:

In [28]: df[last_row.argsort()]
Out[28]: 
        aaa       ppp       fff       ddd
0  0.328281  0.375458  1.188905  0.503059
1  0.305457  0.186163  0.077681 -0.543215
2  0.684265  0.681724  0.210636 -0.532685
3 -1.134292  1.832272  0.067946  0.250131
4 -0.834393  0.010211  0.649963 -0.551448
5 -1.032405 -0.749949  0.442398  1.274599

利润!

Answer 2

sort_values给定axis=1参数时,该方法直接执行此操作.

sorted_df = df.sort_values(df.last_valid_index(), axis=1)

因此,不再需要将数据帧转置为按行排序.此外,该sort方法现已弃用.