iris_color_select.py

from bokeh.layouts import row, widgetbox
from bokeh.models import ColumnDataSource, LinearColorMapper, Select, ColorBar
from bokeh.plotting import figure, curdoc
from bokeh.palettes import Viridis256
from bokeh.sampledata import iris

df = iris.flowers

data_options = sorted(df.columns)[:-1]

p = figure(plot_height=400, plot_width=500, toolbar_location=None, id='fig')

# Select widgets
x_select = Select(title='X axis', options=data_options, value=data_options[0])
y_select = Select(title='Y axis', options=data_options, value=data_options[1])
color_select = Select(title='Color', options=data_options, value=data_options[2])

selector_dict = {'x': x_select, 'y': y_select}


def update_source(attr, old, new, column):
    # choose which select widget to look at
    selector = selector_dict[column]
    # make a dictionary of the column and new data
    data_update_dict = {column: df[selector.value]}
    # update the source
    source.data.update(data_update_dict)


def update_color(attr, old, new):
    source.data.update({'color': df[color_select.value]})
    color_mapper.high = df[color_select.value].max()
    color_mapper.low = df[color_select.value].min()

# set the on_change functions
x_select.on_change('value', lambda attr, old, new: update_source(attr, old, new, column = 'x'))
y_select.on_change('value', lambda attr, old, new: update_source(attr, old, new, column = 'y'))
color_select.on_change('value', update_color)


color_mapper = LinearColorMapper(low=df[color_select.value].min(),
                                 high=df[color_select.value].max(),
                                 palette=Viridis256,
                                 id='cmpr')

source = ColumnDataSource({'x': df[x_select.value],
                           'y': df[y_select.value],
                           'color': df[color_select.value]})
 

# add circle glyphs
r = p.circle('x', 'y',
             size=8,
             color={'field': 'color', 'transform': color_mapper},
             source=source, id='circles')

color_bar = ColorBar(color_mapper=color_mapper,
                     label_standoff=5,
                     location=(10, 0))

# put the pieces together
p.add_layout(color_bar, 'right')
controls = widgetbox([x_select, y_select, color_select],
                     width=200)
layout = row(controls, p)

curdoc().add_root(layout)

Plot changes size when petal_length is chosen to color the glyphs. Does not occur for any other column.