How to handle widget events using PyQt signal and slot mechanism
Signals & Slots Signals and slots are used for communication between objects. The signals and slots mechanism is a central feature of Qt and probably the part that differs most from the features provided by other frameworks.
signal-slot-mp·PyPI
signal-slot enables a parallel programming paradigm inspired by Qt's signals and slots, but in Python.
How Qt Signals and Slots Work - Part 2 - Qt5 New Syntax
Qt Designer also allows you to preview your GUIs using different styles and resolutions, connect signals and slots, create menus and toolbars, and more.