Refactoring: Simple GUI application

We have a working code, but is it ready? What are the next steps? How can we make it better? Let’s see some tips and tricks.

Covered topics

• Imports
• Line length
• Typing
• Separation of responsibilities
• Extracting methods
• (Naming)

🎥 Video recording

Q:\08_DOCS\005_Oktatás_Kurzus\01_ECON\003PythonTipsAndTricks\VIDEO\2025_02_20_Refactoring_example.mp4

Refactor basics

The original code (the non-refactored) can be found in the old folder.
The refactored version is in the new folder.

What does the program do?

Opens a GUI where we can add persons’ data to a json file, the gui can show those persons and filter them.

Running

Create a virtual environment and install the requirments.txt, then
python new/main.py
or
python old/main.py

What is the issue with old version?

• Line length (more than 80-100 chars)
• No __name__ == “__main__” used
• Everything is in one file! What actually?
  • Start of the program
  • GUI
  • The logic for adding, reading and saving Person
  • The Person is just a dictionary

What are the changes?

There is a system design for most of the GUIs: MVC (Model - View - Control)

Model defines the objects of our program this time the Person.
View is the GUI itself.
Control handles the communication between View and Model.

In the end it is not just a design for GUIs but can also work for Webapps, since the website we are watching is giving the look,
the backend is the control and the model is the database where the data is mostly hold.

Seperate the individual functions of the program

• GUI -> Shows us a window and displays Person
• Person -> Make it a class for better understanding
• Person Managing -> If we move logic from the GUI this is what we get
• Create config for better handling of static json path

Final thoughts

This refactoring is not the best, may not suit for everyone. But this way the code is seperated and easy to adding functionality, finding bugs.
It may require more ‘learning’ for the first time reading it, but if we start off like this it is much easier to work with it.

The message of the refactor could be two point at the end:

• D.R.Y. -> Don’t Repeat Yourself
• Seperation -> A piece of code (function, method, class) should only have 1 functionallity that is in it’s name.
  
  Also, even if you are not going to publish the code or only you will use your code for 100% even then,
  write requirments.txt for best compatibility, because if you move the directory the venv will not work anymore and must set up a new one.