When saving a pandas dataframe to csv how do I retain the columns.name?

Question

Initial Problem

When I run the following in ipython

import numpy as np
import pandas as pd

df = pd.DataFrame(np.round(9*np.random.rand(4,4), decimals=1))
df.index.name = 'x'
df.columns.name = 'y'

df.to_csv('output.csv')

df

it outputs the following result:

y    0    1    2    3
x                    
0  7.6  7.4  0.3  7.5
1  5.6  0.0  1.5  5.9
2  7.1  2.1  0.0  0.9
3  3.7  6.6  3.3  8.4

However when I open output.csv the "y" is removed:

x   0   1   2   3
0   7.6 7.4 0.3 7.5
1   5.6 0   1.5 5.9
2   7.1 2.1 0   0.9
3   3.7 6.6 3.3 8.4

How do I make it so that the df.columns.name is retained when I output the dataframe to csv?

Crude workaround

Current crude work-around is me doing the following:

df.to_csv('output.csv', index_label = 'x|y')

Which results in output.csv reading:

x|y 0   1   2   3
0   7.6 7.4 0.3 7.5
1   5.6 0   1.5 5.9
2   7.1 2.1 0   0.9
3   3.7 6.6 3.3 8.4

Something better would be great! Thanks for your help (in advance).

Context

This is what I am working on: https://github.com/SimonBiggs/Electron-Cutout-Factors

This is an example table: https://github.com/SimonBiggs/Electron-Cutout-Factors/blob/master/output/20140807_173714/06app06eng/interpolation-table.csv

Solution 1

You can pass a list to name the columns, then you can specify the index name when you are writing to csv:

df.columns = ['column_name1', 'column_name2', 'column_name3']
df.to_csv('/path/to/file.csv', index_label='Index_name')

Solution 2

How about this? It's slightly different but hopefully usable, since it fits the CSV paradigm:

>>> df.columns = ['y{}'.format(name) for name in df.columns]
>>> df.to_csv('output.csv')
>>> print open('output.csv').read()
x,y0,y1,y2,y3
0,3.5,1.5,1.6,0.3
1,7.0,4.7,6.5,5.2
2,6.6,7.6,3.2,5.5
3,4.0,2.8,7.1,7.8

Comments

[SimonBiggs]

Thanks for the offer, unfortunately that doesn't meet my needs. I care about the numbers that are written in the columns and index.

[John Zwinck]

Can you be more specific about what problem my solution causes you? It seems like what you're asking for will otherwise require you to write your own header rows before asking Pandas to write the body of the CSV. You can do that if you really need to.

[SimonBiggs]

First: I want the code to be as readable and transparent as possible. So minimal complication is important. Second: I am creating a look-up table to be used for interpolation. The axes represent "width" and "aspect ratio", hence the headings. The full code can be seen at my gihtub here. An example of one of these interpolation tables can be seen here.

[John Zwinck]

I think your "crude workaround" is as good as you're likely to get.

[SimonBiggs]

Okay, thanks John. Also, for future readers, the table link has changed. An example table should now be able to be found here