Pandas style object with multi-index

问题

I am formatting a pandas dataframe with styler to highlight columns and format numbers. I also want to apply multi-index for more clear, pleasant and easy to read. Since I apply Styler to subset of columns it does not work work with the multi-index.

Example:

arrays = [np.hstack([['One']*2, ['Two']*2]) , ['A', 'B', 'C', 'D']]
columns = pd.MultiIndex.from_arrays(arrays)
data =  pd.DataFrame(np.random.randn(5, 4), columns=list('ABCD'))
data.columns = columns 
import seaborn as sns
cm = sns.light_palette("green", as_cmap=True)
data.style.background_gradient(cmap=cm, subset=['A'])

Is there a way to subset the columns so the styler can work. According to the below sources this is implemented but there is not examples so it is hard to me to understand how to apply it: http://pandas.pydata.org/pandas-docs/stable/generated/pandas.formats.style.Styler.html https://github.com/pandas-dev/pandas/issues/11655

thank you !

回答1:

I think you can use pd.IndexSlice[...] method:

data.style.background_gradient(cmap=cm, subset=pd.IndexSlice[:, pd.IndexSlice[:, 'A']])

Demo:

In [5]: data.loc[pd.IndexSlice[:, pd.IndexSlice[:, 'A']]]
Out[5]:
        One
          A
0 -0.808483
1  0.009371
2  0.977138
3 -0.875554
4 -0.052424

In [6]: data
Out[6]:
        One                 Two
          A         B         C         D
0 -0.808483 -2.280683  0.576145  0.649688
1  0.009371  0.721510  1.013764 -0.157493
2  0.977138  1.441392  1.718618 -0.320826
3 -0.875554 -1.060507  1.457075  0.570195
4 -0.052424 -0.742842 -0.203830 -1.202091

in Jupyter:

回答2:

Here, is another way:

data.style.background_gradient(cmap=cm, subset=data.columns.get_loc_level('A', level=1)[0])

Output:

回答3:

If you know what the hierarchy of the index is, for example that 'A' is under 'One' you can use a tuple to reference the column.

data.style.background_gradient(cmap=cm, subset=[('One','A')])

Then the table will be displayed as above.

Should you want to style more than one column with a multi-index you need to provide a list of tuples ie

arrays = [np.hstack([['One']*2, ['Two']*2]) , ['A', 'B', 'C', 'D']]
columns = pd.MultiIndex.from_arrays(arrays)
data =  pd.DataFrame(np.random.randn(5, 4), columns=list('ABCD'))
data.columns = columns 
cm = sns.light_palette("green", as_cmap=True)
data.style.background_gradient(cmap=cm, subset=[('One','A'),('Two','C')])

Displays like this

来源：https://stackoverflow.com/questions/41738175/pandas-style-object-with-multi-index

标签

python

pandas

styles

subset

multi-index