How to update plot by setting source with Select widget in bokeh

Question

I have 2 pandas dataframes, with identical column names. I try to update my plot based on the bokeh Select widget.

app.py

from bokeh.models import ColumnDataSource
from bokeh.plotting import figure, output_file, show, output_notebook
from bokeh.models.widgets import Select
from bokeh.io import curdoc
from bokeh.layouts import column, row

import pandas as pd

d1 = {'time': [1,2,3,4], 'y': [2,4,6,8]}
d2 = {'time': [1,2,3,4,5], 'y': [2,1,1,8,22]}
df1 = pd.DataFrame(data=d1, )
df2 = pd.DataFrame(data=d2, )

source = ColumnDataSource(df1 )

p = figure()
r = p.vbar(x='time', top='y', width=1,
         source = source)

select = Select(title="monthly csv-s",  options=['d1', 'd2'])

def update_plot(attrname, old, new):
    if select.value == 'd1':
        newSource = df1
    if select.value == 'd2':
        newSource = df2
    source.data =  newSource 


select.on_change('value', update_plot)
layout = column(row(select, width=400), p)
curdoc().add_root(layout)

I try to run this using bokeh serve --show app.py I got the following error when I use the Select widget:

error handling message Message 'PATCH-DOC' (revision 1): ValueError('expected an element of ColumnData(String, Seq(Any)), got time y\n0 1 2\n1 2 1\n2 3 1\n3 4 8',)

Can you help me with that?

Michael · Accepted Answer · 2017-10-19 14:10:39Z

4

Following this example, you need to set source.data to be a dict, not a DataFrame. So your new code for update_plot() would be:

def update_plot(attrname, old, new):
    if select.value == 'd1':
        newSource = d1  # changed this to the dict
    if select.value == 'd2':
        newSource = d2  # changed this to the dict
    source.data =  newSource

answered Oct 19, 2017 at 14:10

Michael

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2 Comments

user3598726 Over a year ago

Thanks, my data is from a csv d1, d2 are present only in my dummy example, but df.to_dict('list') was able to solve my problem.

InLaw Over a year ago

i get the error

Error running application handler <bokeh.application.handlers.script.ScriptHandler object at 0x7fc47ea98b70>: Cannot run the event loop while another loop is running File "base_events.py", line 417, in run_forever .. 200 GET /test_bokeh_app (127.0.0.1) 130.17ms

, but the app appears to work.

InLaw · Accepted Answer · 2019-11-11 14:30:32Z

0

if you are working with joined data frames and manipulate on the outcome, it would be easier to not refer to an raw source element (like the dict):

def update_plot(attrname, old, new):
   if select.value == 'd1':
       newSource =  ColumnDataSource(df1) 
   if select.value == 'd2':
       newSource =  ColumnDataSource(df2) 
   source.data = newSource.data

answered Nov 11, 2019 at 14:30

InLaw

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