pandas styling add attribute for cell/column

Question

I need to color specific columns in the table and convert it to html. I know it's possible to apply pandas styling to required subsets of data; for example, the next code snippet seems to work just fine. But the problem is that I need to set the same styling using bgcolor html attribute, not CSS. And I have found only Styler.set_table_attributes, which doesn't really help in my case. My current approach: I'm converting the html obtained from pandas to BeautifulSoup and adding attributes there, but it's not really convenient.

import numpy as np
import pandas as pd

np.random.seed(0)
df = pd.DataFrame(np.random.randn(10,4), columns=['A','B','C','D'])
st = df.style

def highlight(c):    
    color = 'green' if (c > 0) else 'red'
    return f'background-color:{color}'

st.applymap(highlight, subset=['C', 'D'])

with open('out.html','w') as f:
        f.write(str(st.to_html()))

# how i'm doing this now:
from bs4 import BeautifulSoup
res = BeautifulSoup(df.to_html(index=False), features='html.parser')

for header in ['C', 'D']:    
    index = df.columns.get_loc(header)
    
    for tr in res.table.tbody.select('tr'):
        td = tr.select('td')[index]
        c = float(td.text)
        td.attrs['bgcolor'] = 'green' if (c > 0) else 'red'

with open('out2.html','w') as f:
        f.write(str(res))

Answer 1

You can set the bgcolor attribute using pandas styling by defining a custom function that returns the bgcolor attribute in an HTML style tag. You can then use this function with the Styler.applymap() method to apply the styling to the required subset of data.

Example:

import numpy as np
import pandas as pd

np.random.seed(0)
df = pd.DataFrame(np.random.randn(10,4), columns=['A','B','C','D'])
st = df.style

def highlight(c):
    color = 'green' if (c > 0) else 'red'
    return f'bgcolor: {color}'

st.applymap(highlight, subset=['C', 'D'])

with open('out.html','w') as f:
    f.write(st.to_html())

The render() method of the Styler object will return the styled DataFrame as an HTML string with the bgcolor attribute set using the style tag.