如何仅对 pandas 数据框中的某些列进行排序? [英] how to sort only some of the columns in a data frame in pandas?
问题描述
有没有一种方法可以以用户定义的方式对列表中的某些元素进行排序?
Is there a way to sort only some elements of a list in a user-defined manner?
import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.rand(5, 6), columns=['x','a','c','y','b','z'])
我想对df的列进行排序，使前3列为[x, y, z](按此顺序)，而其余列的放置位置无关紧要.
I'd like to sort the columns of df in a way that the first 3 columns are [x, y, z] (in this order), and it doesn't matter where the remaining columns are placed.
在此示例中，我可以手动执行此操作，但是随着列表的增加，使用更合适的方法会很方便.
For this example I could do it manually, but as the list gets bigger it would be convenient to use a more appropriate method.
我考虑过使用l = df_r.columns.tolist()，但是即使只有一个列表，我也无法弄清楚该怎么做...
I thought of using l = df_r.columns.tolist() but I can't figure out how to this it even with a single list...
推荐答案
如果您知道要按特定顺序排列几列，只需对所有列和预排序的列进行设置区别，然后调用
If you know that you want a few columns in a specific order, just do a set difference between all columns and the pre-ordered columns, then call reindex:
In [13]: cols = list('xacybz')
In [14]: df = DataFrame(randn(10, len(cols)), columns=cols)
In [15]: preordered = list('xyz')
In [16]: new_order = preordered + list(df.columns - preordered)
In [17]: new_order
Out[17]: ['x', 'y', 'z', 'a', 'b', 'c']
In [18]: df.reindex(columns=new_order)
Out[18]:
x y z a b c
0 -0.012 0.949 -0.276 -0.074 -0.054 0.541
1 0.994 1.059 -0.158 0.267 -0.590 0.263
2 -0.632 -0.015 -0.097 -1.904 -1.351 -1.105
3 -0.730 -0.684 -0.226 2.664 -0.385 1.727
4 0.891 -0.602 3.426 1.529 0.853 -0.451
5 -0.471 0.689 1.170 -0.635 -0.663 0.180
6 1.536 0.793 1.461 0.723 -0.795 -1.094
7 0.417 0.787 1.676 1.563 1.412 0.398
8 0.378 1.436 -0.024 0.293 0.655 -0.113
9 -0.159 -0.416 -1.526 0.633 -0.780 -0.613
preorder的元素以什么顺序出现并不重要:
It won't matter what order the elements of preorder occur in:
In [25]: shuffle(df.columns.values)
In [26]: df
Out[26]:
b a z c x y
0 -0.054 -0.074 -0.276 0.541 -0.012 0.949
1 -0.590 0.267 -0.158 0.263 0.994 1.059
2 -1.351 -1.904 -0.097 -1.105 -0.632 -0.015
3 -0.385 2.664 -0.226 1.727 -0.730 -0.684
4 0.853 1.529 3.426 -0.451 0.891 -0.602
5 -0.663 -0.635 1.170 0.180 -0.471 0.689
6 -0.795 0.723 1.461 -1.094 1.536 0.793
7 1.412 1.563 1.676 0.398 0.417 0.787
8 0.655 0.293 -0.024 -0.113 0.378 1.436
9 -0.780 0.633 -1.526 -0.613 -0.159 -0.416
In [27]: new_order = preordered + list(df.columns - preordered)
In [28]: new_order
Out[28]: ['x', 'y', 'z', 'a', 'b', 'c']
这篇关于如何仅对 pandas 数据框中的某些列进行排序?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
