iintroduction the tkinter library github introduction to objects the class __init__ method variables inside class collections of classes inheritance derived classes created with revised methods multiple inheritance drawing rectangle and square visibility of variables properties local variables types in python summary programs on github visual programming in python importing fewer names creating an object-oriented version using message boxes using file dialogs understanding options for the pack layout manager using the ttk libraries responding to user input adding two numbers catching the error applying colors in tkinter creating radio buttons using class-level variable communicating between classes using the grid layout creating checkbuttons disabling check boxes