Issue after updating to Panel 1.0: Plotly chart not updating to display most recent data from select widget when using panel.serve


I have been very exited of the latest release of panel (1.0) and all of its new features and Bokeh 3 support. It has been amazing to witness development of this library.

On last Thursday I had to immediately test how a project that I am currently developing is running on it.

I have been writing code for a program that has a selector where you can choose an area and a pie chart that displays data from selected area. The problem is that program doesn’t render the most recently selected value and shows pie chart based on the previously selected value when it is run by panel.serve.

I have bound the chart to a select widget and it works well when I do display it inside a Jupyter notebook. When served from Jupyter by panel.serve() on a separate window plotly chart gets rendered by using values from the previously selected value from the Select widget.

I am not sure if it the problem is on my code, but same type of code worked well on previous version. I haven’t found any solution on how to fix this even though I have tried other bindings methods explained in current documentation.

I would be again grateful for any hints that would push me to right direction on solving this issue.

Code below can be used to demonstrates the problem.

import pandas as pd
import panel as pn
import as px

# Define data for pie chart and selector by creating a dataframe
data = [["NWA", 2, 3, 4],
        ["NWB", 6, 8, 3],
        ["RCA", 2, 3, 7],
        ["DNO", 7, 8, 1]]

source_df = pd.DataFrame(data, columns=['Area', 'pop_A', 'pop_B', 'pop_C'])
source_df.set_index("Area", inplace=True)

# Modify data to use as plotly pie chart source 
tr_source_df = source_df.transpose()
tr_source_df['AreaName'] = tr_source_df.index

# Define Pie chart
def create_plotly_pie(selectorvalue):
    # Define data source
    pie_source = tr_source_df
    # Define plot colours
    colormap = {'pop_A': '#7570b3', 'pop_B': '#e7298a', 'pop_C': '#1b9e77'}
    # Define pie chart
    fig = px.pie(pie_source, values=selectorvalue, names='AreaName', color='AreaName',
    # Define mouse hover info
    # Make chart responsive
    fig.layout.autosize = True
    # Return figure
    return fig

# Selector 
# Define dropdown selector to select data for pie chart 
selector = pn.widgets.Select(
    name='Choose an area', 

# Define selector UI
selector_row = pn.Row(selector, height=100)

# Create pie chart by binding it to the selector
def present_plotly_pie(selectorvalue):
    pie_chart = create_plotly_pie(selectorvalue)
    return pn.pane.Plotly(pie_chart, config={'responsive': True, 'displayModeBar': False}, margin = (0,0,0,0))

# Serve selector and pie chart UI
#pn.serve(pn.Column(selector_row, pn.Row(present_plotly_pie, height=300)))

# OR

# Display it on notebook
pn.Column(selector_row, pn.Row(present_plotly_pie, height=300))

Hello gnuza, did you find a solution? I’m having a similar problem…

Hello everyone,
I’m currently using version 1.1.0 of Panel and I’m facing a similar issue. As already mentioned the chart does not display the most recently selected value; instead, it shows the chart based on the previously selected value. This issue specifically occurs with Plotly (I am with version 5.15.0), whereas Matplotlib or Seaborn work correctly. It appears to be a compatibility problem between Panel>=1.0 and Plotly.

Hi Davide_sd. I couldn’t make it work with Plotly, gave up trying and changed plotting library to echarts, which works the way I did expect the selector to work. It took some time to understand echarts, but I am happy with the results.

Thanks svvoronin for testing it with Matplotlib and Seaborn.

This Panel Plotly issue must be a bug and I have to learn how to report it.