Utilizing asynchronous signal notifications
Flask has a built-in lightweight event-driven mechanism called signals that can establish a loosely coupled software architecture using subscription-based event handling. It can trigger single or multiple transactions depending on the purpose. The blinker module provides the building blocks for Flask signal utilities, so install blinker using the pip command if it is not yet in the virtual environment.
Flask has built-in signals and listens to many Flask events and callbacks such as render_template(), before_request(), and after_request(). These signals, such as request_started, request_finished, message_flashed, and template_rendered, are found in the flask module. For instance, once a component connects to template_rendered, it will run its callback method after render_template() finishes posting a Jinja template. However, our target is to create custom asynchronous signals.
To create custom signals, import the Namespace class from...
