Jupyter Widgets: Sending Custom Event To Backend From Frontend

Jupyter Widgets can have a separate frontend and backend component. Sometimes, you need to send a message from one to the other. This example shows the basics on sending a message from the frontend to the backend.

In your Widget’s backend (Python) code, listen for the custom event from the frontend:

    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.on_msg(self._handle_custom_msg)

    def _handle_custom_msg(self, content, buffers):
        if content['event'] == 'another_important_event':
            print(content['value'])

Now, in the Widget’s frontend (Javascript) code, send the message as needed:

    sendMessageToBackend: function() {
        this.model.send({event: 'another_important_event', value: 'green'});
    },

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