Class CallbackContext

dash/_callback_context.py:54–355

# pylint: disable=no-init
class CallbackContext:
    @property
    @has_context
    def inputs(self):
        return getattr(_get_context_value(), "input_values", {})

    @property
    @has_context
    def states(self):
        return getattr(_get_context_value(), "state_values", {})

    @property
    @has_context
    def triggered(self):
        """
        Returns a list of all the Input props that changed and caused the callback to execute. It is empty when the
        callback is called on initial load, unless an Input prop got its value from another initial callback.
        Callbacks triggered by user actions typically have one item in triggered, unless the same action changes
        two props at once or the callback has several Input props that are all modified by another callback based on
        a single user action.

        Example:  To get the id of the component that triggered the callback:
        `component_id = ctx.triggered[0]['prop_id'].split('.')[0]`

        Example:  To detect initial call, empty triggered is not really empty, it's falsy so that you can use:
        `if ctx.triggered:`
        """
        # For backward compatibility: previously `triggered` always had a
        # value - to avoid breaking existing apps, add a dummy item but
        # make the list still look falsy. So `if ctx.triggered` will make it
        # look empty, but you can still do `triggered[0]["prop_id"].split(".")`
        return getattr(_get_context_value(), "triggered_inputs", []) or falsy_triggered

    @property
    @has_context
    def triggered_prop_ids(self):
        """
        Returns a dictionary of all the Input props that changed and caused the callback to execute. It is empty when
        the callback is called on initial load, unless an Input prop got its value from another initial callback.
        Callbacks triggered by user actions typically have one item in triggered, unless the same action changes
        two props at once or the callback has several Input props that are all modified by another callback based
        on a single user action.

        triggered_prop_ids (dict):
        - keys (str) : the triggered "prop_id" composed of "component_id.component_property"
        - values (str or dict): the id of the component that triggered the callback. Will be the dict id for pattern matching callbacks

        Example - regular callback
        {"btn-1.n_clicks": "btn-1"}

        Example - pattern matching callbacks:
        {'{"index":0,"type":"filter-dropdown"}.value': {"index":0,"type":"filter-dropdown"}}

        Example usage:
        `if "btn-1.n_clicks" in ctx.triggered_prop_ids:
            do_something()`
        """
        triggered = getattr(_get_context_value(), "triggered_inputs", [])