BUG: Multiple CSS selectors using set_table_styles and dict form of table_styles

[AndrewLister-STFC]

• I have checked that this issue has not already been reported.

• I have confirmed this bug exists on the latest version of pandas.

• I have confirmed this bug exists on the master branch of pandas.

Reproducible Example

import pandas as pd
df = pd.DataFrame([range(5) for _ in range(5)], columns=list('abcde'))
styled = df.style.set_table_styles({
    'b': [{'selector': 'th, td', 'props': [('border-left', '2px solid black')]}]
})
# styled = df.style.set_table_styles({
#     'b': [{'selector': 'th', 'props': [('border-left', '2px solid black')]},
#           {'selector': 'td', 'props': [('border-left', '2px solid black')]}]
# })
html = styled.render()
with open('css_style_bug.html', 'w') as f:
    f.write(html)

Issue Description

This is a minor issue when styling a table for html display. When setting a table style for a specified column using set_table_styles, the column is only applied to the final selector tag if they are named in a comma seperated list.

This seems to be similar to issue #34061.

Expected Behavior

I have commented out, in the above examples, a workaround which does the expected behaviour.

Installed Versions

INSTALLED VERSIONS

commit : 73c6825
python : 3.8.10.final.0
python-bits : 64
OS : Linux
OS-release : 5.4.72-microsoft-standard-WSL2
Version : #1 SMP Wed Oct 28 23:40:43 UTC 2020
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : C.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.3.3
numpy : 1.21.2
pytz : 2021.3
dateutil : 2.8.2
pip : 20.0.2
setuptools : 44.0.0
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.0.2
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : None
fsspec : None
fastparquet : None
gcsfs : None
matplotlib : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
numba : None

[attack68]

Yes this seems to be true in master also.

If anyone wants to do a fix this is quite easy:

1. import _format_table_styles from styler_render in style.py (actually change from private '_' method to a regular non-underscored methods)
2. change line 2052 from for s in styles to for s in _format_table_styles(styles)
3. Add relavent bug fix whats new and add a relevant test, probably in the same place as the fix for BUG: using a list in "selector" for set_table_styles produces wrong rules #34061.

[mabittar]

hello can I help with this one??

I did the changes needs in steps 1 and 2, but need some advice with step 3.
Where to insert the bug_fix information and where would be the most suitable place to insert a new style test? I put it next to the other tests regarding borders and colors, near to line 818 in test_style
and how i run tests.io? ->already find: make test-scripts

[attack68]

@mabittar I just realised the test you did for this PR didn't actually test the bug: which was that this failed when using the dict input form, and the test doesn't use the dict input form.

Any chance you want to tidy it up? :)