Python Learning¶

This guide explains a complete Python program — a small shop manager — line by line. The program uses tkinter to open a window where you can add, edit and delete products, record sales and see a sales report. Everything is saved to shop_data.json.

The 146-line source is split into eight parts. Each part shows its code first, then explains every line, then lists where its names are used elsewhere, and ends with practice questions.

Contents¶

1. 1. Imports and the data file

   Lines 1–6

2. 2. The Shop class: creating, saving and loading

   Lines 8–26

3. 3. Adding, editing and deleting products

   Lines 28–48

4. 4. Recording sales and the report

   Lines 50–63

5. 5. The window and the input form

   Lines 65–75

6. 6. Reading the form, run() and the button handlers

   Lines 77–111

7. 7. Refreshing the table and selecting a row

   Lines 113–127

8. 8. Buttons, the table and starting the program

   Lines 129–146

What each button does¶

Every button follows the same path: click → run → button handler → Shop method → save to file → refresh the table.

Index of names¶

Every name defined in the program, the line where it is defined and the lines that use it.