ui.update_select

ui.update_select(id, *, label=None, choices=None, selected=None, session=None)

Change the value of a select input on the client.

Parameters

id : str

An input id.

label : Optional[TagChild] = None

An input label.

choices : Optional[SelectChoicesArg] = None

Either a list of choices or a dictionary mapping choice values to labels. Note that if a dictionary is provided, the keys are used as the (input) values. A dictionary of dictionaries is also supported, and in that case, the top-level keys are treated as <optgroup> labels.

selected : Optional[str | list[str]] = None

The values that should be initially selected, if any.

session : Optional[Session] = None

A Session instance. If not provided, it is inferred via get_current_session.

Note

The input updater functions send a message to the client, telling it to change the
settings of an input object. The messages are collected and sent after all the
observers (including outputs) have finished running.

The syntax of these functions is similar to the functions that created the inputs in
the first place. For example, [](:func:`~shiny.ui.input_numeric`) and
[](:func:`~shiny.ui.update_numeric`) take a similar set of arguments.

Any arguments with ``None`` values will be ignored; they will not result in any
changes to the input object on the client.

For [](:func:`~shiny.ui.update_radio_buttons`), [](:func:`~shiny.ui.update_checkbox_group`), and
[](:func:`~shiny.ui.update_select`), the set of choices can be cleared by using ``choices=[]``.
Similarly, for these inputs, the selected item can be cleared by using
`selected=[]`.

See Also

Examples

#| standalone: true
#| components: [editor, viewer]
#| layout: vertical
#| viewerHeight: 400

## file: app.py
from shiny import App, Inputs, Outputs, Session, reactive, ui

app_ui = ui.page_fluid(
    ui.tags.p("The checkbox group controls the select input"),
    ui.input_checkbox_group(
        "inCheckboxGroup", "Input checkbox", ["Item A", "Item B", "Item C"]
    ),
    ui.input_select("inSelect", "Select input", ["Item A", "Item B", "Item C"]),
)


def server(input: Inputs, output: Outputs, session: Session):
    @reactive.effect
    def _():
        x = input.inCheckboxGroup()

        # Can use [] to remove all choices
        if x is None:
            x = []
        elif isinstance(x, str):
            x = [x]

        ui.update_select(
            "inSelect",
            label="Select input label " + str(len(x)),
            choices=x,
            selected=x[len(x) - 1] if len(x) > 0 else None,
        )


app = App(app_ui, server)