Knob Examples and Reference

Default Knob

An example of a default Knob without any extra properties.

from dash import Dash, html, Input, Output, callback
import dash_daq as daq

app = Dash()

app.layout = html.Div([
    daq.Knob(id='my-knob-1'),
    html.Div(id='knob-output-1')
])

@callback(Output('knob-output-1', 'children'), Input('my-knob-1', 'value'))
def update_output(value):
    return f'The knob value is {value}.'

if __name__ == '__main__':
    app.run(debug=True)

Size

Set the size(diameter) of the knob in pixels with size.

import dash_daq as daq

daq.Knob(
    size=140,
    value=3
)

Max

Set the maximum value of the knob using max.

import dash_daq as daq

daq.Knob(
    max=100,
    value=3
)

Color Ranges

Control color ranges with:

color={
    'ranges':{
        '<color>':[<value>,<value>],
        '<color>':[<value>,<value>],
        '<color>':[<value>,<value>]
        }
    }

import dash_daq as daq

daq.Knob(
  label="Color Ranges",
  value=3,
  color={"ranges":{"green":[0,5],"yellow":[5,9],"red":[9,10]}}
)

Color Gradient

Set up a color gradient with:

color={
    'gradient':True,
    'ranges':{
        '<color>':[<value>,<value>],
        '<color>':[<value>,<value>],
        '<color>':[<value>,<value>]
    }
}

import dash_daq as daq

daq.Knob(
  label="Gradient Ranges",
  value=7,
  color={"gradient":True,"ranges":{"green":[0,5],"yellow":[5,9],"red":[9,10]}}
)

Scale

Adjust the scale interval, label interval, and start of the scale with scale.

import dash_daq as daq

daq.Knob(
  label="Scale",
  value=7,
  max=18,
  scale={'start':0, 'labelInterval': 3, 'interval': 3}
)

Knob Properties

Access this documentation in your Python terminal with:
```python

help(dash_daq.Knob)
```

Our recommended IDE for writing Dash apps is Dash Enterprise’s
Data Science Workspaces,
which has typeahead support for Dash Component Properties.
Find out if your company is using
Dash Enterprise.

id (string; optional):
The ID used to identify this compnent in Dash callbacks.

value (number; optional):
The value of knob.

color (dict; optional):
Color configuration for the knob’s track.

color is a string | dict with keys:

  • default (string; optional):
    Color used for current value text and other minor accents.

  • gradient (boolean; optional):
    Display ranges as a gradient between given colors.

  • ranges (dict; optional):
    Define multiple color ranges on the knob’s track. The key
    determines the color of the range and the value is the start,end
    of the range itself. Ranges must be contiguous along the entirety
    of the knob’s range of values.

    ranges is a dict with keys:

    • color (list of numbers; optional)

size (number; optional):
The size (diameter) of the knob in pixels.

min (number; default 0):
The minimum value of the knob.

max (number; default 10):
The maximum value of the knob.

disabled (boolean; optional):
If True, knob cannot be moved.

theme (dict; default light):
Theme configuration to be set by a ThemeProvider.

label (dict; optional):
Description to be displayed alongside the control. To control styling,
pass an object with label and style properties.

label is a string | dict with keys:

  • label (string; optional)

  • style (dict; optional)

labelPosition (a value equal to: ‘top’ or ‘bottom’; default 'top'):
Where the knob label is positioned.

scale (dict; optional):
Configuration for the component scale.

scale is a dict with keys:

  • custom (dict; optional):
    Custom scale marks. The key determines the position and the value
    determines what will show. If you want to set the style of a
    specific mark point, the value should be an object which contains
    style and label properties.

    custom is a number | dict with keys:

    • label (string; optional)

    • style (string; optional)

  • interval (number; optional):
    Interval by which the scale goes up. Attempts to dynamically
    divide min-max range by default.

  • labelInterval (number; optional):
    Interval by which labels are added to scale marks. Defaults to 2
    (every other mark has a label).

  • start (number; optional):
    Value to start the scale from. Defaults to min.

className (string; optional):
Class to apply to the root component element.

style (dict; optional):
Style to apply to the root component element.

persistence (boolean | string | number; optional):
Used to allow user interactions in this component to be persisted when
the component - or the page - is refreshed. If persisted is truthy
and hasn’t changed from its previous value, a value that the user
has changed while using the app will keep that change, as long as the
new value also matches what was given originally. Used in
conjunction with persistence_type.

persisted_props (list of values equal to: ‘value’; default ['value']):
Properties whose user interactions will persist after refreshing the
component or the page. Since only value is allowed this prop can
normally be ignored.

persistence_type (a value equal to: ‘local’, ‘session’ or ‘memory’; default 'local'):
Where persisted user changes will be stored: memory: only kept in
memory, reset on page refresh. local: window.localStorage, data is
kept after the browser quit. session: window.sessionStorage, data is
cleared once the browser quit.