Book a Demo!
CoCalc Logo Icon
StoreFeaturesDocsShareSupportNewsAboutPoliciesSign UpSign In
holoviz
GitHub Repository: holoviz/panel
 Path: blob/main/doc/how_to/interactivity/bind_function.md
2011 views

Add interactivity to a function

This guide addresses how to make your functions interactive by binding widgets to them. This is done with the use of pn.bind, which allows binding the value of a widget to a function or method.

The recommended approach to adding interactivity to your applications is by writing reactive functions or methods. To discover how to write one of these first, we need a function.

Let's start by creating a function. The function takes an argument number and will return a string of stars equal to the number:

def star_creator(number):
    return "⭐" * number

star_creator(5)

Calling a function repeatedly with different arguments is not very interactive, so as a second step we will create a widget. Here we have chosen the pn.widgets.IntSlider with a value of 5 and a range between 1 and 10:

import panel as pn

pn.extension()

slider = pn.widgets.IntSlider(value=5, start=1, end=10)
slider

To make our star_creator function interactive we can now bind the widget to the function and add it to a layout together with the slider:

interactive_star_creator = pn.bind(star_creator, slider)

pn.Column(slider, interactive_star_creator)

:::{note} pn.bind works very similarly to Python's functools.partial, except that it automatically resolves the current value of any widgets, Parameters and other bound functions that are passed as arguments. :::

Internally the layout will create a so called ParamFunction component to wrap the interactive function. This wrapper component will re-evaluate and update the output whenever the inputs to the function change.