Be sure that camera_shop.py, input_validation.py, and dans_camera_shop.db are all in the same directory. Then,
simply run camera_shop.py either in an IDE or through the terminal. This program's user interface is entirely through
the terminal, and all directions are given therein.
NOTE: if you want to save changes to the database, be sure you exit the program through the menu options. If you terminate the program by typing CTRL+C or clicking STOP in the IDE, any changes you make will not be saved in the database file.
To simplify input validation, I created a python file to store some functions that I knew I would use repeatedly in my program. This includes functions that get dates, phone numbers, integers, and more from the user.
For the main functionality of the program, there are several nested loops, and tons of nested if statements. This all combines to create the user interface, which contains several menus, and different options within those menus. I use sqlite to perform all database operations, and some pandas/numpy for retrieving information to show to the user. At the end of my program, sqlite saves all changes made into the database file, so it is stored long-term.
All data was fabricated by myself. I actually wrote the majority of the program first, and then killed two birds with one stone, by using my program to add data to my database, while debugging/troubleshooting at the same time to find issues. My input validation ensured that all data entered into the database is clean.
I use CROSS JOIN operations throughout my program to combine related data. Also, I prevent the user from deleting any data that would cause errors with related data. Specifically, if a user tries to delete a product or customer that is associated with a sale, the operation is stopped and the program informs the user that they need to delete the associated first. When a user deletes a sale, that sale is deleted from the sale_info table, and also all orders with that ID are deleted from the sale_orders table.