Exam 13: Video Games: Multithreading, Event Handlers, Static Variables

Case Study 2: 1. import turtle 2. 3. class Etch: 4. def __init__(self): 5. self.__myT = turtle.Turtle() 6. self.__myScreen = turtle.Screen() 7. self.__myT.color('blue') 8. self.__myT.pensize(2) 9. self.__myT.speed(0) 10. self.__distance = 5 11. self.__turn = 10 ... 19. def fwd(self): 20. self.__myT.forward(self.__distance) -Refer to the session in the accompanying Case Study 2. The Etch class uses the inheritance approach to working with a turtle.

Explain how to set up a callback for mouse events on the turtle.

What is the main structure of an event-driven program?

Match each definition with its term. -Hides any functions from outside of the class and starts with __.

Match each definition with its term. -First-come first-served data structure.

Passing ____ to a turtle function that is used to register a callback effectively cancels the callback mechanism.

What are some of the benefits of extending a class from Thread?

Case Study 1: 1. class EventHandler: 2. def __init__(self): 3. self.__queue = [] 4. self.__eventKeeper = {} 5. 6. def addEvent(self, eventName): 7. self.__queue.append(eventName) 8. 9. def registerCallback(self, event, func): 10. self.__eventKeeper[event] = func 11. 12. def run(self): 13. while(True): 14. if len(self.__queue) > 0: 15. nextEvent = self.__queue.pop(0) 16. self.__eventKeeper[nextEvent]() 17. else: 18. print('queue is empty') -Refer to the session in the accompanying Case Study 1. What kind of loop is shown on lines 13-18?

Match each definition with its term. -A special instruction to the Python interpreter that starts with @.

Describe the __moveOneStep method of the AnimatedTurtle class presented in your text. What is the significance of the two underscores in the method name?

Match each definition with its term. -Variable that is shared by all instances of a class and is available to all the methods in the class.

What is the name of the event loop for a turtle?

A(n) ____ variable is shared by all instances of the class.

Typically, desktop applications are single-threaded.

Before using the screen to respond to keyboard events, call the ____ method of Screen.

Case Study 2: 1. import turtle 2. 3. class Etch: 4. def __init__(self): 5. self.__myT = turtle.Turtle() 6. self.__myScreen = turtle.Screen() 7. self.__myT.color('blue') 8. self.__myT.pensize(2) 9. self.__myT.speed(0) 10. self.__distance = 5 11. self.__turn = 10 ... 19. def fwd(self): 20. self.__myT.forward(self.__distance) -Refer to the session in the accompanying Case Study 2. Explain the composition approach used by the Etch class.

How do you make a class multithreaded in Python?

The main difference between keyboard callbacks and mouse callbacks is that the function we write to accept mouse callbacks must accept two parameters.

To hide a function from use outside of the class, begin the name with:

How would you detect when two turtles collide?