Question

Problem 3: A Connect Four Player Class

In this problem, you will create a Player class to represent a player of the Connect Four game. In combination with the Board class that you wrote in Problem 2 and some code that you will write in the next problem set, this will enable you to play a game of Connect Four with a friend!

Getting started

Begin by downloading the file ps11pr3.py and opening it in Sypder or your editor of choice. Make sure that you put the file in the same folder as your ps11pr2.py file.

Note: We have included an import statement at the top of ps11pr3.py that imports the Board class from your ps11pr2.py file. Therefore, you will be able to use Board objects and their methods as needed.

Your tasks

Implement the Player class in ps11pr3.py by completing the tasks described below.

Important

If you add test code to your ps11pr3.py file, please put it in one or more separate test functions, which you can then call to do the testing. Having test functions is not required. However, you should not have any test code in the global scope (i.e., outside of a function). See the note in Problem 2 for more detail.

1. Write a constructor __init__(self, checker) that constructs a new Player object by initializing the following two attributes:

• an attribute checker – a one-character string that represents the gamepiece for the player, as specified by the parameter checker

• an attribute num_moves – an integer that stores how many moves the player has made so far. This attribute should be initialized to zero to signify that the Player object has not yet made any Connect Four moves.

Begin your __init__ with an assert statement like the one that we recommended for the is_win_for method in Problem 2.

2. Write a method __repr__(self) that returns a string representing a Player object. The string returned should indicate which checker the Player object is using. For example:

>>> p1 = Player('X')
>>> p1
Player X
>>> p2 = Player('O')
>>> p2
Player O

The results of your __repr__ method should exactly match the results shown above. Remember that your __repr__ method should return a string. It should not do any printing.

3. Write a method opponent_checker(self) that returns a one-character string representing the checker of the Player object’s opponent. The method may assume that the calling Player object has a checker attribute that is either 'X' or 'O'.

For example:

>>> p = Player('X')
>>> p.opponent_checker()
'O'

Important: Make sure that your return values are uppercase letters, and that you do not accidentally use a lowercase letter or a zero instead of an uppercase 'O'.

4. Write a method named next_move(self, board) that accepts a Board object as a parameter and returns the column where the player wants to make the next move. To do this, the method should ask the user to enter a column number that represents where the user wants to place a checker on the board. The method should repeatedly ask for a column number until a valid column number is given.

Additionally, this method should increment the number of moves that the Player object has made.

Notes:

• To determine whether a given column number is valid, you should make use a method in the Board class that you implemented in Problem 1.

• In order to get input from the user, you should use the input function. Because input always returns a string, you will need to convert the returned string to an integer to get a column number that you can work with.

Example:

In the example below, the underlining is for distinguishing user input. The input you give in your program should not be underlined.

>>> p = Player('X')
>>> b1 = Board(6, 7)    # valid column numbers are 0 - 6
>>> p.next_move(b1)
Enter a column: -1
Try again!
Enter a column: 7
Try again!
Enter a column: 5
5                      # return value of method call
>>> p.num_moves        # number of moves was updated
1

Answer 1

Code:

#ps11pr3.py:

from ps11pr2 import Board

class Player:

    def __init__(self, checker):

       

        assert(checker == 'X' or checker == 'O')

        self.checker = checker

        self.num_moves = 0

    def __str__(self):

        if self.checker == 'X':

            return 'Player X'

        else:

            return 'Player O'

    def __repr__(self):

        return str(self)

       

    def opponent_checker(self):

        if self.checker == 'X':

            return 'O'

        else:

            return 'X'

    def next_move(self, board):

        self.num_moves += 1

       

        while True:

            col = int(input('Enter a column: '))

            if board.can_add_to(col) == True:

                return col

            else:

                print('Try again!')

Output: