Multiple Signals And Slots Python

A simple implementation of the Signal/Slot pattern. I originally uploaded this to ASPN's python cookbook in 2005. To use, simply create a Signal instance and connect methods, which act as the 'slot' in this design pattern. The instance of signal is self-sufficient; it doesn't have to be a member of a class. The signal and slot operation are used to handle events and signals of the objects or widgets at the python app development level. It will also enable communication between some designed objects. The following steps are needed for creating a Python signal and slot operations.

Graphical applications (GUI) are event-driven, unlike console or terminal applications. A users action like clicks a button or selecting an item in a list is called an event.

If an event takes place, each PyQt5 widget can emit a signal. A signal does not execute any action, that is done by a slot.

Related course:
Create GUI Apps with PyQt5

Signals and slot introduction
Consider this example:

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The button click (signal) is connected to the action (slot). In this example, the method slot_method will be called if the signal emits.

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This principle of connecting slots methods or function to a widget, applies to all widgets,

or we can explicitly define the signal:

PyQt supports many type of signals, not just clicks.

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Example
We can create a method (slot) that is connected to a widget. A slot is any callable function or method.

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On running the application, we can click the button to execute the action (slot).

If you are new to programming Python PyQt, I highly recommend this book.