plotly express: additional categorical hover_data shows codes instead of categories

[OlafHaag]

Hello!
I didn't find this issue reported yet. When I add columns from a dataframe of type category to the hover_data of a plotly express figure, codes instead of the categories are shown.
It took me a while to figure this out, because I had numeric categories close to their codes. This is an easy pitfall. Once you remove a category, the numbers aren't as expected anymore, because the codes changed.

import pandas as pd
import plotly.express as px

df = pd.DataFrame({'x': [1,2,1,2,1,2],
                   'y': [1,1,2,2,3,3],
                   'user': [1,1,2,2,3,3],
                   'color': ['color1', 'color1', 'color2', 'color2', 'color3', 'color3'],
                   'foo': ['a','b','a','b','a','b'],
                   'bar': [2,2,2,3,3,3]})

df[['user', 'color', 'foo', 'bar']] = df[['user', 'color', 'foo', 'bar']].astype('category')
# Fails to show foo and bar categories. Shows codes instead.
hover1 = {'x': False, 'foo':  True, 'bar': True}
fig1 = px.line(data_frame=df, x='x', y='y', line_group='user', color='color', hover_data=hover1)
fig1.show()

# Workaround.
hover2 = {'x': False, 'foo_':  (True, df['foo'].values), 'bar_': (True, df['bar'].values)}
fig2 = px.line(data_frame=df, x='x', y='y', line_group='user', color='color', hover_data=hover2, labels={'foo_': 'foo', 'bar_': 'bar'})
fig2.show()

plotly v4.9.0

[emmanuelle]

Thanks for reporting this. This is not related to the dict mode of hover_data, since the code below also shows the same faulty behaviour

import pandas as pd
import plotly.express as px

df = pd.DataFrame({'x': [1,2,1,2,1,2],
                   'y': [1,1,2,2,3,3],
                   'user': [1,1,2,2,3,3],
                   'color': ['color1', 'color1', 'color2', 'color2', 'color3', 'color3'],
                   'foo': ['a','b','a','b','a','b'],
                   'bar': [2,2,2,3,3,3]})

df[['user', 'color', 'foo', 'bar']] = df[['user', 'color', 'foo', 'bar']].astype('category')
# Fails to show foo and bar categories. Shows codes instead.

fig1 = px.scatter(data_frame=df, x='x', y='y', color='color', hover_data=['foo', 'bar'])
fig1.show()

[gvwilson]

Hi - we are trying to tidy up the stale issues and PRs in Plotly's public repositories so that we can focus on things that are still important to our community. Since this one has been sitting for several years, I'm going to close it; if it is still a concern, please add a comment letting us know what recent version of our software you've checked it with so that I can reopen it and add it to our backlog. Thanks for your help - @gvwilson