User feedback

When a user initiates some action on the server, it’s often helpful to provide feedback on its progress, or additional information about what’s happening. This page will cover three different ways to give user’s feedback with shiny: notifications, progress bars, and confirmation modals.

Note

The examples on this page use asynchronous programming. This ensures long-running or sleeping code does not stall the shiny server.

(It is also necessary for running examples in the browser.)

Notifications

Use ui.notification_show() to display a message in the corner of the screen. Try clicking “Show” in the example below to see two messages pop up in sequence.

#| standalone: true
#| components: [editor, viewer]
#| layout: vertical

from shiny import App, reactive, ui
from asyncio import sleep

app_ui = ui.page_fluid(
    ui.input_action_button("show", "Show"),
)

def server(input, output, session):

    @reactive.Effect
    @reactive.event(input.show)
    async def _():
        ui.notification_show("Message")
        await sleep(1)
        ui.notification_show("Warning message", type="warning")


app = App(app_ui, server, debug=True)

Note that the example above simply waits a second between messages. In practice you might have messages provide updates during long running calculations.

Progress bars

Use ui.Progress() to create a progress bar, that can be updated to show how far along a task is. Try clicking “Compute” below to see the progress bar fill over time.

#| standalone: true
#| components: [editor, viewer]
#| layout: vertical

from shiny import App, reactive, render, ui
from asyncio import sleep


app_ui = ui.page_fluid(
    ui.input_action_button("button", "Compute"),
    ui.output_text("compute"),
)

def server(input, output, session):

    @output
    @render.text
    @reactive.event(input.button)
    async def compute():
        with ui.Progress(min=1, max=15) as p:
            p.set(message="Calculation in progress", detail="This may take a while...")

            for i in range(1, 15):
                p.set(i, message="Computing")
                await sleep(0.1)

        return "Done computing!"


app = App(app_ui, server)

Note that ui.Progress() is a context manager, so should be used as part of a with statement.

Confirming with modals

Use ui.modal() to cover the page with an instructional overlay.

#| standalone: true
#| components: [editor, viewer]
#| layout: vertical

from shiny import App, reactive, ui

app_ui = ui.page_fluid(
    ui.input_action_button("show", "Show modal dialog"),
)

def server(input, output, session):

    @reactive.Effect
    @reactive.event(input.show)
    def _():
        m = ui.modal(
            "This is a somewhat important message.",
            title="Somewhat important message",
            easy_close=True,
            footer=None,
        )
        ui.modal_show(m)


app = App(app_ui, server)