Continuing my journey on Qt and PyQt, I was interested in how to structure medium to large sized applications with this technology (and Desktop applications for Python in general). I came across some blogs about Python with MVC, MVP and MVVM but nothing substantial in larger examples. I also discovered that PySide6 may be the better way to go due to license and official support.

What is MVVM?

I was first exposed to the Model-View-ViewModel (MVVM) pattern while working in C# and WPF years ago and has felt like the more modular and maintainable of the three. Per Microsoft (https://learn.microsoft.com/en-us/dotnet/architecture/maui/mvvm).

There are three core components in the MVVM pattern: the model, the view, and the view model. Each serves a distinct purpose. The diagram below shows the relationships between the three components.

Summary Comparison

• MVC: Emphasizes separation of concerns with distinct roles for Model, View, and Controller. Common in web development.

• MVP: Focuses on testability and a clear separation between UI representation (View) and UI logic (Presenter). Widely used in desktop and mobile applications.

• MVVM: Utilizes data binding to create a direct connection between the View and ViewModel, simplifying UI logic and improving maintainability. Popular in applications with data-binding frameworks.

Application Overview

In this article, we will build a simple Desktop application using PySide6 widgets, with a simple list on the left pane and a main content area on the right. The corresponding view is displayed in the main content area when you select the list item on the left.

File Structure

I chose to create sub-packages for model, view and viewmodel sections to keep organized in some manner. I am running "main.py" in debug mode to launch.

Components

The following is a summary of the items developed within this application.

Menu bar and Toolbar

This demonstrates the basic file menu. One notable element is the use of "qtawesome" for the icons, which made it painless to include.

PySide6 uses QActions which make it

About Dialog

A simple modal prompt as a makeshift about box.

Themes

PySide6 supports themes. This application provides a simple example of both light and dark themes. For the moment, this is hard-coded, but intent is to tie the setting to the "Preferences" dialog.

Preferences Dialog

Views

Drive Simulator

A simple representation of a motor drive and pid controller to demonstrate use of QChart and basic controls.

Rich Textbox Editing

Demonstrates basic use of QTextEdit with common toolbar.

Dummy

The simplest MVVM component.

Code

Repository: https://github.com/ericjameszimmerman/pyside6-mvvm-example

v0.1.0: https://github.com/ericjameszimmerman/pyside6-mvvm-example/releases/tag/0.1.0