An Introduction to Interactive Programming in Python - Week two

Event handlers — Event-driven programming

• Event handlers (also called callbacks) are functions registered to an event such as a button click, keyboard press or mouse click.
• Event handlers react to the event by changing the state (collection of information) encoded in the program.
• Lecture examples - Events
• More examples - None

Local variables — Local vs. global variables

• Assignment to a variable inside a Python function creates a local variable.
• The scope of variable (portion of the program where the value of the variable can be accessed) is the body of function.
• Lecture examples - Local vs Global
• More examples - Example

Global variables — Local vs. global variables

• Variables defined outside functions are global variables. Their values may be accessed inside functions without declaration.
• To modify to a global variable inside a function, the variable must be declared inside the function using the keyword global.
• Global variables are a convenient (but dangerous) way for event handlers to share information in event-driven programming.
• Lecture examples - Local vs Global
• More examples - Example

SimpleGUI module — SimpleGUI

• Special module for CodeSkulptor that supports 2D interactive applications. The Docs button links to documentation for SimpleGUI.
• SimpleGUI allows creations of frames and timers as well as loading sounds and images.
• Frames include a control panel (with buttons and input fields), a status area (for monitoring keyboard and mouse events) and a canvas (with simple 2D drawing operations).
• Lecture examples - SimpleGUI, Template
• More examples - Layout, Frame, Errors

Buttons — Buttons

• Buttons may be created (and their event handlers registered) via add_button.
• Buttons are positioned linearly (top/down) in the control panel in their order of creation.
• Lecture examples - Calculator, Buttons
• More examples - Structure, Canvas Color, Prize Boxes, True-False Quiz

Input fields — Input fields

• Input fields may be created (and their event handlers registered) via add_input.
• Input fields are positioned linearly (top/down) in the control panel in their order of creation.
• The event handlers for the input field take a single parameter that is the text string entered.
• Lecture examples - Calculator, Input Fields
• More examples - Structure, Functions, Factoring, Silly Words

Programming Tips — Week 2

from: https://class.coursera.org/interactivepython-005/wiki/view?page=week2