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

Question 1

Which of the following parts of an event-driven program are managed by a game maker rather than by the Python event handler?

A) Multithreading
B) Queue
C) Event loop
D) Callback function

Answer 1

D

Question 2

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

A) Event loop
B) Queue
C) Callback function
D) Event processing

Answer 2

A

Question 3

A ____ is a data structure that works like a to-do list.

A) list
B) set
C) queue
D) dictionary

Answer 3

C

Question 4

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 is held in self.__queue?

A) The list of events that need to be processed
B) The dictionary that maps events to their callback functions
C) The list of how many times the simulation should run
D) The number of different types of callback functions

Question 5

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. How would you call the function associated with the key 'mouse'?

A) self.__queue['mouse']
B) self.__eventKeeper['mouse']()
C) self.__eventKeeper('mouse')
D) self.__queue('mouse')

Question 6

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?

A) Definite
B) Abstract
C) Multithreaded
D) Infinite

Question 7

How do you make a class multithreaded in Python?

A) Inherit from Thread.
B) Import threading.
C) Include an instance variable named thread.
D) Include a method named threaded().

Question 8

In a multithreaded class, the ____ method creates a new thread and calls the run method of the class inside that new thread.

A) sleep
B) start
C) run
D) thread

Question 9

The ____ function causes the thread to pause for the number of seconds passed as a parameter.

A) thread.pause
B) thread.rest
C) time.sleep
D) time.pause

Question 10

The turtle module's ____ method is used to register callbacks for mouse events.

A) mouse
B) onmouse
C) mouseclick
D) onclick

Question 11

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

A) listen
B) onkey
C) main
D) start

Question 12

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

A) run
B) main
C) mainloop
D) eventloop

Question 13

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

A) stop
B) None
C) 0
D) turtle

Question 14

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

A) an x.
B) one underscore.
C) two underscores.
D) one "at" symbol.

Question 15

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

A) instance
B) multithreaded
C) event
D) static

Question 16

A queue enforces a first-come first-served strategy for handling events.

Question 17

Typically, desktop applications are single-threaded.

Question 18

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.

Question 19

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

Question 20

A Python-mangled name that is hidden outside its class starts with a @.

Question 21

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

A) Queue
B) Static variable
C) Decorator
D) Name mangling

Question 22

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.

A) Queue
B) Static variable
C) Decorator
D) Name mangling

Question 23

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

A) Queue
B) Static variable
C) Decorator
D) Name mangling

Question 24

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

A) Queue
B) Static variable
C) Decorator
D) Name mangling

Question 25

Describe the overall structure of an event-driven program.

Question 26

Explain the difference between a single thread of execution and multithreading.

Question 27

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

Question 28

What callback registration functions does the turtle module provide?

Question 29

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.

Question 30

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

Question 31

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

Question 32

How would you detect when two turtles collide?

Question 33

Describe the static method in the video game presented in your text. What is special about static methods?