Widgets are interactive controls that can be added to Bokeh applications to provide a front end user interface to a visualization. They can drive new computations, update plots, and connect to other programmatic functionality. When used with the Bokeh server, widgets can run arbitrary Python code, enabling complex applications. Widgets can also be used without the Bokeh server in standalone HTML documents through the browser’s Javascript runtime.
To use widgets, you must add them to your document and define their callbacks. Widgets can be added directly to the document root or nested inside a layout. There are two ways to use a widget’s functionality:
A CustomJS callback (see JavaScript Callbacks). This approach will work in standalone HTML documents or Bokeh server apps. Use bokeh serve to start a Bokeh server and set up event handlers with .on_change (or for some widgets, .on_click).
A CustomJS callback (see JavaScript Callbacks). This approach will work in standalone HTML documents or Bokeh server apps.
CustomJS
Use bokeh serve to start a Bokeh server and set up event handlers with .on_change (or for some widgets, .on_click).
bokeh serve
.on_change
.on_click
Event handlers are Python functions that users can attach to widgets. These functions are then called when certain attributes on the widget are changed. The function signature of event handlers is determined by how they are attached to widgets (e.g. whether by .on_change or .on_click).
All widgets have an .on_change method that takes an attribute name and one or more event handlers as parameters. These handlers are expected to have the function signature, (attr, old, new), where attr refers to the changed attribute’s name, and old and new refer to the previous and updated values of the attribute.
(attr, old, new)
attr
old
new
def my_text_input_handler(attr, old, new): print("Previous label: " + old) print("Updated label: " + new) text_input = TextInput(value="default", title="Label:") text_input.on_change("value", my_text_input_handler)
Additionally, some widgets, including the button, dropdown, and checkbox, have an .on_click method that takes an event handler as its only parameter. For a plain Button, this handler is called without parameters. For the other widgets with .on_click, the handler is passed the new attribute value.
Button
def my_radio_handler(new): print 'Radio button option ' + str(new) + ' selected.' radio_group = RadioGroup(labels=["Option 1", "Option 2", "Option 3"], active=0) radio_group.on_click(my_radio_handler)
Bokeh provides a simple default set of widgets. Users can create their own custom widgets, or wrap different third party widget libraries by creating custom extensions as described in Extending Bokeh.
For more information about the attributes to watch using .on_change, see the Reference. (Information about widgets is found under bokeh.models.)
The sections below collect short but complete examples of using all the built-in widgets. Many of the examples print output that can be observed by looking at your browser Javascript console log.
Bokeh provides a simple Button:
from bokeh.io import show from bokeh.models import Button, CustomJS button = Button(label="Foo", button_type="success") button.js_on_click(CustomJS(code="console.log('button: click!', this.toString())")) show(button)
Bokeh also provides a checkbox button group, that can have multiple options selected simultaneously:
from bokeh.io import show from bokeh.models import CheckboxButtonGroup, CustomJS LABELS = ["Option 1", "Option 2", "Option 3"] checkbox_button_group = CheckboxButtonGroup(labels=LABELS, active=[0, 1]) checkbox_button_group.js_on_click(CustomJS(code=""" console.log('checkbox_button_group: active=' + this.active, this.toString()) """)) show(checkbox_button_group)
A standard checkbox:
from bokeh.io import show from bokeh.models import CheckboxGroup, CustomJS LABELS = ["Option 1", "Option 2", "Option 3"] checkbox_group = CheckboxGroup(labels=LABELS, active=[0, 1]) checkbox_group.js_on_click(CustomJS(code=""" console.log('checkbox_group: active=' + this.active, this.toString()) """)) show(checkbox_group)
A widget to allow the user to specify an RGB color value.
from bokeh.io import show from bokeh.layouts import column from bokeh.models import ColorPicker from bokeh.plotting import Figure plot = Figure(x_range=(0, 1), y_range=(0, 1), plot_width=350, plot_height=350) line = plot.line(x=(0,1), y=(0,1), color="black", line_width=4) picker = ColorPicker(title="Line Color") picker.js_link('color', line.glyph, 'line_color') show(column(plot, picker))
Bokeh provides a sophisticated data table widget based on SlickGrid. Note that since the table is configured with a data source object, any plots that share this data source will automatically have selections linked between the plot and the table (even in static HTML documents).
from datetime import date from random import randint from bokeh.io import show from bokeh.models import ColumnDataSource, DataTable, DateFormatter, TableColumn data = dict( dates=[date(2014, 3, i+1) for i in range(10)], downloads=[randint(0, 100) for i in range(10)], ) source = ColumnDataSource(data) columns = [ TableColumn(field="dates", title="Date", formatter=DateFormatter()), TableColumn(field="downloads", title="Downloads"), ] data_table = DataTable(source=source, columns=columns, width=400, height=280) show(data_table)
A widget to allow the user to specify a date value.
from bokeh.io import show from bokeh.models import CustomJS, DatePicker date_picker = DatePicker(title='Select date', value="2019-09-20", min_date="2019-08-01", max_date="2019-10-30") date_picker.js_on_change("value", CustomJS(code=""" console.log('date_picker: value=' + this.value, this.toString()) """)) show(date_picker)
The Bokeh date range-slider can be configured with start and end date values, a step size, an initial value, and a title:
start
end
step
value
title
from datetime import date from bokeh.io import show from bokeh.models import CustomJS, DateRangeSlider date_range_slider = DateRangeSlider(value=(date(2016, 1, 1), date(2016, 12, 31)), start=date(2015, 1, 1), end=date(2017, 12, 31)) date_range_slider.js_on_change("value", CustomJS(code=""" console.log('date_range_slider: value=' + this.value, this.toString()) """)) show(date_range_slider)
A widget for displaying text that can support HTML in a <div> tag:
from bokeh.io import show from bokeh.models import Div div = Div(text="""Your <a href="https://en.wikipedia.org/wiki/HTML">HTML</a>-supported text is initialized with the <b>text</b> argument. The remaining div arguments are <b>width</b> and <b>height</b>. For this example, those values are <i>200</i> and <i>100</i>, respectively.""", width=200, height=100) show(div)
A button that displays a drop-down list of mutually exclusive items when clicked.
from bokeh.io import show from bokeh.models import CustomJS, Dropdown menu = [("Item 1", "item_1"), ("Item 2", "item_2"), None, ("Item 3", "item_3")] dropdown = Dropdown(label="Dropdown button", button_type="warning", menu=menu) dropdown.js_on_event("menu_item_click", CustomJS(code="console.log('dropdown: ' + this.item, this.toString())")) show(dropdown)
A widget allowing users to choose a file and store its contents.
from bokeh.io import show from bokeh.models import FileInput file_input = FileInput() show(file_input)
A multi-select widget to present multiple available options in a compact horizontal layout:
from bokeh.io import show from bokeh.models import CustomJS, MultiChoice OPTIONS = ["foo", "bar", "baz", "quux"] multi_choice = MultiChoice(value=["foo", "baz"], options=OPTIONS) multi_choice.js_on_change("value", CustomJS(code=""" console.log('multi_choice: value=' + this.value, this.toString()) """)) show(multi_choice)
A multi-select widget to present multiple available options in vertical list:
from bokeh.io import show from bokeh.models import CustomJS, MultiSelect OPTIONS = [("1", "foo"), ("2", "bar"), ("3", "baz"), ("4", "quux")] multi_select = MultiSelect(value=["1", "2"], options=OPTIONS) multi_select.js_on_change("value", CustomJS(code=""" console.log('multi_select: value=' + this.value, this.toString()) """)) show(multi_select)
A widget for displaying a block of text in an HTML <p> tag:
from bokeh.io import show from bokeh.models import Paragraph p = Paragraph(text="""Your text is initialized with the 'text' argument. The remaining Paragraph arguments are 'width' and 'height'. For this example, those values are 200 and 100, respectively.""", width=200, height=100) show(p)
A text input that obscures the entered text:
from bokeh.io import show from bokeh.models import CustomJS, PasswordInput password_input = PasswordInput(placeholder="enter password...") password_input.js_on_change("value", CustomJS(code=""" console.log('password_input: value=' + this.value, this.toString()) """)) show(password_input)
A widget for displaying a block of pre-formatted text in an HTML <pre> tag:
from bokeh.io import show from bokeh.models import PreText pre = PreText(text="""Your text is initialized with the 'text' argument. The remaining Paragraph arguments are 'width' and 'height'. For this example, those values are 500 and 100, respectively.""", width=500, height=100) show(pre)
A radio button group can have at most one selected button at a time:
from bokeh.io import show from bokeh.models import CustomJS, RadioButtonGroup LABELS = ["Option 1", "Option 2", "Option 3"] radio_button_group = RadioButtonGroup(labels=LABELS, active=0) radio_button_group.js_on_click(CustomJS(code=""" console.log('radio_button_group: active=' + this.active, this.toString()) """)) show(radio_button_group)
A radio group uses standard radio button appearance:
from bokeh.io import show from bokeh.models import CustomJS, RadioGroup LABELS = ["Option 1", "Option 2", "Option 3"] radio_group = RadioGroup(labels=LABELS, active=0) radio_group.js_on_click(CustomJS(code=""" console.log('radio_group: active=' + this.active, this.toString()) """)) show(radio_group)
The Bokeh range-slider can be configured with start and end values, a step size, an initial value, and a title:
from bokeh.io import show from bokeh.models import CustomJS, RangeSlider range_slider = RangeSlider(start=0, end=10, value=(1,9), step=.1, title="Stuff") range_slider.js_on_change("value", CustomJS(code=""" console.log('range_slider: value=' + this.value, this.toString()) """)) show(range_slider)
A single selection widget:
from bokeh.io import show from bokeh.models import CustomJS, Select select = Select(title="Option:", value="foo", options=["foo", "bar", "baz", "quux"]) select.js_on_change("value", CustomJS(code=""" console.log('select: value=' + this.value, this.toString()) """)) show(select)
The Bokeh slider can be configured with start and end values, a step size, an initial value, and a title:
from bokeh.io import show from bokeh.models import CustomJS, Slider slider = Slider(start=0, end=10, value=1, step=.1, title="Stuff") slider.js_on_change("value", CustomJS(code=""" console.log('slider: value=' + this.value, this.toString()) """)) show(slider)
A numeric spinner widget:
import numpy as np from bokeh.io import show from bokeh.layouts import column, row from bokeh.models import Spinner from bokeh.plotting import figure x = np.random.rand(10) y = np.random.rand(10) p = figure(x_range=(0, 1), y_range=(0, 1)) points = p.scatter(x=x, y=y, size=4) spinner = Spinner(title="Glyph size", low=1, high=40, step=0.5, value=4, width=80) spinner.js_link('value', points.glyph, 'size') show(row(column(spinner, width=100), p))
Tab panes allow multiple plots or layouts to be shown in selectable tabs:
from bokeh.io import show from bokeh.models import Panel, Tabs from bokeh.plotting import figure p1 = figure(plot_width=300, plot_height=300) p1.circle([1, 2, 3, 4, 5], [6, 7, 2, 4, 5], size=20, color="navy", alpha=0.5) tab1 = Panel(child=p1, title="circle") p2 = figure(plot_width=300, plot_height=300) p2.line([1, 2, 3, 4, 5], [6, 7, 2, 4, 5], line_width=3, color="navy", alpha=0.5) tab2 = Panel(child=p2, title="line") show(Tabs(tabs=[tab1, tab2]))
A widget for collecting multiple lines of text from a user:
from bokeh.io import show from bokeh.models import CustomJS, TextAreaInput text_area_input = TextAreaInput(value="default", rows=6, title="Label:") text_area_input.js_on_change("value", CustomJS(code=""" console.log('text_area_input: value=' + this.value, this.toString()) """)) show(text_area_input)
A widget for collecting a line of text from a user:
from bokeh.io import show from bokeh.models import CustomJS, TextInput text_input = TextInput(value="default", title="Label:") text_input.js_on_change("value", CustomJS(code=""" console.log('text_input: value=' + this.value, this.toString()) """)) show(text_input)
The toggle button holds an on/off state:
from bokeh.io import show from bokeh.models import CustomJS, Toggle toggle = Toggle(label="Foo", button_type="success") toggle.js_on_click(CustomJS(code=""" console.log('toggle: active=' + this.active, this.toString()) """)) show(toggle)