Action Button

#| standalone: true
#| components: [viewer]
#| viewerHeight: 200

## file: app.py
from shiny import App, reactive, render, ui

app_ui = ui.page_fluid(
    ui.row(
        ui.column(6, ui.input_action_button("action_button", "Increase Number")),
        ui.column(6, ui.output_text("counter").add_class("display-5 mb-0")),
        {"class": "vh-100 justify-content-center align-items-center px-5"},
    ).add_class("text-center")
)

def server(input, output, session):
    count = reactive.value(0)

    @reactive.effect
    @reactive.event(input.action_button)
    def _():
        count.set(count() + 1)

    @render.text
    def counter():
        return f"{count()}"

app = App(app_ui, server)

Express
Core

from shiny import reactive, render
from shiny.express import input, ui

ui.input_action_button("action_button", "Action")  

@render.text()
@reactive.event(input.action_button)
def counter():
    return f"{input.action_button()}"

from shiny import App, reactive, render, ui

app_ui = ui.page_fluid(
    ui.input_action_button("action_button", "Action"),  
    ui.output_text("counter"),
)

def server(input, output, session):
    @render.text()
    @reactive.event(input.action_button)
    def counter():
        return f"{input.action_button()}"

app = App(app_ui, server)

Relevant Functions

ui.input_action_button
ui.input_action_button(id, label, *, icon=None, width=None, **kwargs)
reactive.event
reactive.event(*args, ignore_none=True, ignore_init=False)

Details

An action button appears as a button and has a value that increments each time the user presses the button.

Follow these steps to add an action button to your app:

Add ui.input_action_button() to the UI of your app to create an action button. Where you call this function will determine where the button will appear within the app’s layout.
Specify the id and label parameters of ui.input_action_button() to define the button’s identifier and label.

The value of an input component is accessible as a reactive value within the server() function. To access the value of an action button:

Use input.<action_button_id()> (e.g., input.action_button()) to access the value of the action button. The server value of an action button is an integer representing the number of clicks.