As requested by Professor, now the application saves the data on the SQLite database.
In the first post ([here][1]) we did a python program to join three spreadsheets in just one. This work involves knowledge of pandas to organize the data.
Now we create a database and a table to store all data. This version is so simple and does not check the user store option.
I'll create a new project on GitHub because I'll show how to merge these steps in one project. (god to understand git commands line)