express.ui.update_select

express.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[str] = 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 so that the dictionary values can hold HTML labels. 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, input_numeric and 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 update_radio_buttons, update_checkbox_group, and 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 reactive
from shiny.express import input, ui

ui.markdown("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"])


@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,
    )