Homework 8 | CS 88 Fall 2020

Instructions

Download hw08.zip. Inside the archive, you will find starter files for the questions in this homework, along with a copy of the OK autograder.

Submission: When you are done, submit with python3 ok --submit. You may submit more than once before the deadline; only the final submission will be scored. Check that you have successfully submitted your code on okpy.org. See this article for more instructions on okpy and submitting assignments.

Readings: This homework relies on following references:

Section 2.9

Inheritance

Question 1: Errors

It is often said that nothing in life is certain but death and taxes. For a programmer or data scientist, however, nothing is certain but encountering errors.

In Python, there are two primary types of errors, both of which you are likely familiar with: syntax errors and exceptions. Syntax errors occur when the proper structure of the language is not followed, while exceptions are errors that occur during the execution of a program. These include errors such as ZeroDivisionError, TypeError, NameError, and many more!

Under the hood, these errors are based in the concepts of object orientation, and all exceptions are class objects. If you're interested in more detailed explanations of the structure of exceptions as well as how to create your own, check out this article from the Python documentation! In the meantime, we'll implement our own version of an Error class

Complete the Error, SyntaxError, and ZeroDivisionError classes such that they create the correct messages when called.

The SyntaxError and ZeroDivisionError classes inherit from the Error class and add functionality that is unique to those particular errors. Their code is partially implemented for you.
The add_code method adds a new helpful message to your error, while the write method should print the output that you see when an error is raised.
You can access the parent class methods using the super() function

class Error:
    """
    >>> err1 = Error(12, "error.py")
    >>> err1.write()
    error.py:12
    """
    def __init__(self, line, file):
        "*** YOUR CODE HERE ***"

    def format(self):
        return self.file + ':' + str(self.line)

    def write(self):
        print(self.format())

class SyntaxError(Error):
    """
    >>> err1 = SyntaxError(17, "lab10.py")
    >>> err1.write()
    lab10.py:17 SyntaxError : Invalid syntax
    >>> err1.add_code(4, "EOL while scanning string literal")
    >>> err2 = SyntaxError(18, "lab10.py", 4)
    >>> err2.write()
    lab10.py:18 SyntaxError : EOL while scanning string literal
    """
    type = 'SyntaxError'
    msgs = {0 : "Invalid syntax", 1: "Unmatched parentheses", 2: "Incorrect indentation", 3: "missing colon"}

    def __init__(self, line, file, code=0):
        "*** YOUR CODE HERE ***"

    def format(self):
        "*** YOUR CODE HERE ***"

    def add_code(self, code, msg):
        "*** YOUR CODE HERE ***"

class ZeroDivisionError(Error):
    """
    >>> err1 = ZeroDivisionError(273, "lab10.py")
    >>> err1.write()
    lab10.py:273 ZeroDivisionError : division by zero
    """
    type = 'ZeroDivisionError'

    def __init__(self, line, file, message='division by zero'):
        "*** YOUR CODE HERE ***"

    def format(self):
        end = self.type + ' : ' + self.message
        "*** YOUR CODE HERE ***"

Use OK to test your code:

python3 ok -q Error

Use OK to test your code:

python3 ok -q SyntaxError

Use OK to test your code:

python3 ok -q ZeroDivisionError

Election

Let's implement a game called Election. In this game, two players compete to try and earn the most votes. Both players start with 0 votes and 100 popularity.

The two players alternate turns, and the first player starts. Each turn, the current player chooses an action. There are two types of actions:

The player can debate, and either gain or lose 50 popularity. If the player has popularity p1 and the other player has popularity p2, then the probability that the player gains 50 popularity is max(0.1, p1 / (p1 + p2)) Note that the max causes the probability to never be lower than 0.1.
The player can give a speech. If the player has popularity p1 and the other player has popularity p2, then the player gains p1 // 10 votes and popularity and the other player loses p2 // 10 popularity.

The game ends when a player reaches 50 votes, or after a total of 10 turns have been played (each player has taken 5 turns). Whoever has more votes at the end of the game is the winner!

Question 2: Player

First, let's implement the Player class. Fill in the debate and speech methods, that take in another Player other, and implement the correct behavior as detailed above. Here are two additional things to keep in mind:

In the debate method, you should call the provided random function, which returns a random float between 0 and 1. The player should gain 50 popularity if the random number is smaller than the probability described above, and lose 50 popularity otherwise.
Neither players' votes or popularity should ever become negative. If this happens, set it equal to 0 instead.

### Phase 1: The Player Class
class Player:
    """
    >>> reset_random()
    >>> p1 = Player('Hill')
    >>> p2 = Player('Don')
    >>> p1.popularity
    100
    >>> p1.debate(p2)  # random() should return 0.0
    >>> p1.popularity
    150
    >>> p2.popularity
    100
    >>> p2.votes
    0
    >>> p2.speech(p1)
    >>> p2.votes
    10
    >>> p2.popularity
    110
    >>> p1.popularity
    135
    >>> # Additional correctness tests
    >>> p1.speech(p2)
    >>> p1.votes
    13
    >>> p1.popularity
    148
    >>> p2.votes
    10
    >>> p2.popularity
    99
    >>> for _ in range(4):  # 0.1, 0.2, 0.3, 0.4
    ...     p1.debate(p2)
    >>> p2.debate(p1)
    >>> p2.popularity
    49
    >>> p2.debate(p1)
    >>> p2.popularity
    0
    """
    def __init__(self, name):
        self.name = name
        self.votes = 0
        self.popularity = 100

    def debate(self, other):
        "*** YOUR CODE HERE ***"

    def speech(self, other):
        "*** YOUR CODE HERE ***"

    def choose(self, other):
        return self.speech

Use OK to test your code:

python3 ok -q Player

Question 3: Game

Now, implement the Game class. Fill in the play method, which should alternate between the two players, starting with p1, and have each player take one turn at a time. The choose method in the Player class returns the method, either debate or speech, that should be called to perform the action.

In addition, fill in the winner property method, which should return the player with more votes, or None if the players are tied.

### Phase 2: The Game Class
class Game:
    """
    >>> p1, p2 = Player('Hill'), Player('Don')
    >>> g = Game(p1, p2)
    >>> winner = g.play()
    >>> p1 is winner
    True
    >>> # Additional correctness tests
    >>> winner is g.winner
    True
    >>> g.turn
    10
    >>> p1.votes = p2.votes
    >>> print(g.winner)
    None
    """
    def __init__(self, player1, player2):
        self.p1 = player1
        self.p2 = player2
        self.turn = 0

    def play(self):
        while not self.game_over:
            "*** YOUR CODE HERE ***"
        return self.winner

    @property
    def game_over(self):
        return max(self.p1.votes, self.p2.votes) >= 50 or self.turn >= 10

    @property
    def winner(self):
        "*** YOUR CODE HERE ***"

Use OK to test your code:

python3 ok -q Game

Question 4: New Players

The choose method in the Player class is boring, because it always returns the speech method. Let's implement two new classes that inherit from Player, but have more interesting choose methods.

Implement the choose method in the AggressivePlayer class, which returns the debate method if the player's popularity is less than or equal to other's popularity, and speech otherwise. Also implement the choose method in the CautiousPlayer class, which returns the debate method if the player's popularity is 0, and speech otherwise.

### Phase 3: New Players
class AggressivePlayer(Player):
    """
    >>> reset_random()
    >>> p1, p2 = AggressivePlayer('Don'), Player('Hill')
    >>> g = Game(p1, p2)
    >>> winner = g.play()
    >>> p1 is winner
    True
    >>> # Additional correctness tests
    >>> p1.popularity = p2.popularity
    >>> p1.choose(p2) == p1.debate
    True
    >>> p1.popularity += 1
    >>> p1.choose(p2) == p1.debate
    False
    >>> p2.choose(p1) == p2.speech
    True
    """
    def choose(self, other):
        "*** YOUR CODE HERE ***"

class CautiousPlayer(Player):
    """
    >>> reset_random()
    >>> p1, p2 = CautiousPlayer('Hill'), AggressivePlayer('Don')
    >>> p1.popularity = 0
    >>> p1.choose(p2) == p1.debate
    True
    >>> p1.popularity = 1
    >>> p1.choose(p2) == p1.debate
    False
    >>> # Additional correctness tests
    >>> p2.choose(p1) == p2.speech
    True
    """
    def choose(self, other):
        "*** YOUR CODE HERE ***"

Use OK to test your code:

python3 ok -q AggressivePlayer
python3 ok -q CautiousPlayer

Homework 8 Due at 11:59:59 pm on Friday, 11/6/2020.

Instructions

Inheritance

Question 1: Errors

Election

Question 2: Player

Question 3: Game

Question 4: New Players

Homework 8
Due at 11:59:59 pm on Friday, 11/6/2020.