CSCI3180 – Principles of Programming Languages – Spring 2019

Assignment 2 — Your First Date with Python and Duck Typing

Deadline: Mar 10, 2019 (Sunday) 23:59

1 Introduction

The purpose of this assignment is to offer you the first experience with Python, which supports the

object-oriented programming paradigm. Our main focuses are Dynamic Typing and Duck Typing.

Please use Python 3.6 to finish this assignment.

The assignment consists of 4 tasks.

You need to implement a famous board game called Othello in Python.

You are asked to demonstrate the advantages/disadvantages of dynamic typing through some

example code.

We give you the JAVA source code of a game called “The journey”. You need to reimplement

the game in Python to make the code clean with the help of Duck Typing.

Additional features and mechanisms are introduced to the “The journey” game. You need

to implement the enhanced game in both JAVA and Python.

After completing the 4 tasks, you need to write a report elaborating on Dynamic Typing and Duck

Typing.

NOTES: all your codes will be graded on the Linux machines in the Department. You are welcome

to develop your codes on any platform, but please remember to test them on Department machines.

2 Task 1: Othello

This is a small programming exercise for you to get familiar with Python, which is a dynamically

typed language. In this task, you have to strictly follow our proposed OO design and the game

rules for “Othello” stated in this section. For the OO design, you have to follow the prototypes of

the given functions exactly, but can choose to add new member functions. We provide a simple

skeleton for your convenience.

2.1 Description

Othello, also known as Reversi, is a classic board game that involves two players. Two players

take turns in adding their own pieces (discs) in order to flip the opponent’s discs. The game ends

when both players cannot add any more discs onto the board. The player who has more discs on

the board wins the game. It is a tie when the disc numbers of both sides are the same.

2.1.1 Game Rules

The game consists of an 8 × 8 game board with 64 cells. Each cell can hold a disc with two sides:

black and white. In our project, we represent the two sides as follows:

Black side - character O

White side - character X

Players place their discs alternatively on the game board, one using the black side and the

other using the white side. When you place a disc, any opponent’s disc in succession in between

your new disc and another one of your disc will be flipped over to take your color.

As shown in Figure 1, suppose you are the black-disc player and the board on the left shows

the current condition. On the right, the discs with yellow border show the four possible locations

for your next disc, since you can then flip some of your opponent’s discs.

1

Figure 1: Possible moves for Othello

In each turn, a player must place a disc, so that at least one of the opponent’s discs is flipped.

If a player cannot find any location to place a disc, the player has to give up the turn without

placing any disc. A game ends when:

either the board is full, or

no one can make a move, i.e., place a disc.

As shown in Figure 2(a)&(b), the player having more discs of his/her color is the winner. The

game is a tie if the number of white discs equals the number of black discs. Here is a web-based

online Othello game that you can try: https://www.coolmath-games.com/0-reversi.

Figure 2: (a) Player O has won with a fully filled chessboard; (b) Player X has won with a partially

filled chessboard; (c) A tie;

2.2 Game board

The game starts with two black discs and two white discs at the following locations:

Character O at (4,5) and (5,4)

Character X at (4,4) and (5,5)

Other cells are just filled with a single SPACE character. The game always starts with the black

player (‘O’).

CSCI3180作业代做

2.3 Input/Output Specification

The input/output specification is detailed in this section.

2

2.3.1 Input Specification

In this exercise, you are required to use the command line to get input information. Since this is

a simple program, there are just two operations requiring user-input.

Type of Players

Users can choose Player X and Player O to be either human- or computer-controlled. You have

to use the command line to request for the types of the two players before starting the game (as

shown in Figure 3).

Figure 3: Players’ types

Human-Controlled Player’s Move

Human-controlled players require user-inputs to determine their next moves. When it is humancontrolled

player’s turn during the game, your program should request for the row and column of

the next move. The input should be integers from 1 to 8. During each turn, the system will first

check whether there is a legal move for current player. If not, the system will switch to another

player’s turn automatically, as shown in Figure 4(a). Moreover, any invalid input or moves should

be forbidden and the user is requested for input again until a valid move is given. See Figure 4(b)

for an example.

Computer-Controlled Player

A computer-controlled player just randomly chooses an unfilled cell to make a valid move. During

each turn, the system will first check whether there is a legal move for current player. If not, the

system will switch to another player’s turn automatically.

2.4 Python Classes

Please follow the classes Othello, GameBoard, Player, Human and Computer defined below in your

Python implementation. You are free to add other variables, methods or classes. We would start

the program by running the command: python Othello.py

1. Class Othello

A game object which holds the game board, players’ turns and controls game logic. You have

to implement it with the following components:

Instance Variable(s)

gameBoard

- This is an object variable representing the game board.

player1

- This is an object variable representing Player O.

player2

- This is an object variable representing Player X.

turn

3

- This is an integer variable (0 for player1, 1 for player2 ) indicating which player

should play in the current turn.

Figure 4: Example gameplay output. (a) No legal movement; (b) Invalid inputs

Instance Method(s)

__init__(self)

- Create a game board and initialize other instance variables.

createPlayer(self,symbol,playerNum)

- Create a player (human- or computer-controlled) with the corresponding symbol

(’O’ or ’X’) and player number (1 or 2) by prompting the user.

startGame(self)

- Create two players, initialize the game board, and then start a new game and play

until winning/losing or draw.

2. Class GameBoard

You have to implement it with the following components:

Instance Variable(s)

board

- This is an 8 × 8 two-dimensional character array representing the game board.

Instance Method(s)

__init__(self)

- Define all instance variables.

4

init_gameBoard(self)

- Initialize the board. Its initial state is referred to Section 2.2.

execute_flip(self,pos,symbol)

- Flip over all opponent’s symbols in between given position and symbol.

check_legal_move(self,symbol)

- Check whether their is a legal move given symbol.

check_ending(self)

- Check if the game is over.

check_winner(self)

- Count the number for each symbol and return a list, like [17,3]. The first one is

the total number of character ‘O’ and the second one is for character ‘X’.

3. Class Player

An superclass representing a player object. You have to implement it with the following

components:

Instance Variable(s)

playerSymbol

- This is a variable indicating the symbol of the player (X or O).

Instance Method(s)

__init__(self, symbol)

- Initialize the player with its symbol X or O.

nextMove(self, board)

- A method to be implemented in subclasses, which returns a list, like [1,2]. The

first one is the row and the second one is the column (1-8 for each) of the next valid

move. The parameter board represents a two-dimensional character array that represents

the cell conditions in the game board and your function should not modify the array

contents.

4. Class Human and Computer

Classes extending the superclass Player to represent a human- and a computer-controlled

player object respectively.

2.5 Tournament

For this bonus part, you can implement a more brilliant AI player to compete with others. We

will arrange for an automated tournament environment to test your implementations. If you want

to join the tournament, you should submit an additional Python file, named AI_[your SID].py,

like AI_1155123456.py, and the class name is “AI”, which is also extended from the class Player.

The AI strategy should be built in the instance method nextMove(self,board):

The basic requirements have already been mentioned above.

The function must produce an output within one second on the lab’s computers.

You need to test carefully to make sure your code could not damage our test system, e.g.,

the array out of bounds exception!!!

Please note that if your program does not follow any one of the above requirements, you cannot

earn extra points for this project. We will run a round robin tournament. A win is worth 3 points

and a tie is worth 1 point, while a loss score 0 points. The top five entire will receive additional

marks for the assignment: 30, 25, 20, 15, 10, 5 respectively.

5

3 Task 2: Demonstrating Advantages of Dynamic Typing

There are commonly claimed advantages of Dynamic Typing:

1. More generic code can be written. In other words, functions can be defined to apply on

arguments of different types.

2. Possibilities of mixed type collection data structures.

Please provide concise example codes to demonstrate the advantages of Dynamic Typing mentioned

above. You are welcome to provide other advantages and disadvantages along with code

segment for extra bonus points.

Dynamic Typing makes coding more flexible and convenient, but you should bear in mind that

type checking can only be carried out at runtime, incurring time overhead and reliability issues.

4 Task 3: The Journey

This task is also to build a game. A Java program of the game is given. You need to understand

its behavior and re-implement it with Python. After finishing this task, you will have experienced

a special feature of Python called Duck Typing, which is possible only in a dynamically typed

language. And you will see a difference between Java and Python, the former of which does not

support Duck Typing.

4.1 Duck Typing

The following synopsis of Duck Typing is summarized from:

http://en.wikipedia.org/wiki/Ducktyping

http://www.sitepoint.com/making-ruby-quack-why-we-love-duck-typing

In standard statically-typed object-oriented languages, objects’ classes (which determine an object

characteristic and behavior) are essentially interpreted as the objects’ types. Duck Typing is a new

typing paradigm in dynamically-typed (late binding) languages that allow us to dissociate typing

from objects’ characteristics. It can be summarized by the following motto by the late poet James

Whitcombe Riley:

When I see a bird that walks like a duck and swims like a duck and quacks like a duck,

I call that bird a duck.

The basic premise of Duck Typing is simple. If an entity looks, walks, and quacks like a duck, for

all intents and purposes it is fair to assume that one is dealing with a member of the species anas

platyrhynchos. In practical Python terms, this means that it is possible to try calling any method

on any object, regardless of its class.

An important advantage of Duck Typing is that we can enjoy polymorphism without inheritance.

An immediate consequence is that we can write more generic codes, which are cleaner and more

precise.

4.2 Background

In the world of Kafustrok, most of the land is covered in dense forest, populated by bizarre monsters

and a small number of elves. The only safe haven is a small number of villages where humans live.

In order to protect the villages from monster attacks, a selected warrior set foot on the forest to

wipe out all monsters. Every monster has its own territory, and the elves also live in some specific

areas. The warrior can seek help from the elves to heal himself, but he needs to use a certain

amount of magic crystals in exchange.

6

4.3 Task Description

At the beginning, there exists a warrior, e elves and m monsters. All of them will be distributed

in different positions.

? At each iteration, the warrior will try to teleport to a targeted location.

– If meeting a monster, the monster will talk and ask the warrior whether to fight or not.

Yes, if his health is sufficient to kill this monster, with losing certain health, he will

occupy this position and get some magic crystals. Otherwise, he will be killed.

No, enter next iteration.

– If meeting an elf, the elf will talk and ask the warrior whether to make a deal or not.

Yes, he will pay some magic crystals and his health increases with the elf’s magical

power, but cannot exceed the health cap.

No, enter next iteration.

– If nothing is encountered, he will end up in that position.

If all monsters have been killed or the warrior is dead, the game will be over

You should read and execute the given Java program to understand its behavior and design.

Please replicate all the behavior of the given Java Program in Python with Duck Typing, following

the same class design. You should not introduce extra instance variables or instance methods.

Your program should run by calling python the_journey.py. You will also be evaluated on your

programming style.

5 Task 4: More Warriors!

A warrior falls but more warriors stand up. The warriors from different villages form an alliance

and join the journey to destroy the monsters together. Based on the alliance’s agreement, a warrior

needs to share some crystals if the other has a request. Moreover, some life potions appear in the

forest, but their positions always change from time to time, and the warriors can get treatment

if they find the potion. The game still ends when all monsters are eliminated or all warriors are

dead.

5.1 Task Description

At the beginning, there exists w warriors, e elves, m monsters and p life potions. All of them will

be distributed in different positions.

At each iteration, all life potions will teleport into different positions randomly.

At each iteration, all warriors will try to teleport to a targeted location.

For each warrior,

– If meeting a monster, the monster will talk and ask the warrior whether to fight or not.

Yes, if his health is sufficient to kill this monster, with losing certain health, he will

occupy this position and get some magic crystals. Otherwise, he will be killed.

No, enter next iteration.

– If meeting an elf, the elf will talk and ask the warrior whether to make a deal or not.

Yes, he will pay some magic crystals and his health increases with the elf’s magical

power, but cannot exceed the health cap.

No, enter next iteration.

– If meeting a life potion, the warrior will occupy the position and have some health

increased directly. That life potion will disappear.

– If meeting another warrior, then the other warrior will talk and ask the warrior whether

he needs more crystals

7

Yes, he will get some magic crystals for free.

No, enter next iteration.

– If nothing is encountered, he will end up in that position.

If all monsters or warriors have been killed, the game will be over

You are now required to modify/extend both the Java and Python implementation of Task 3. You

will also be evaluated on your programming style.

Figure 5: Example gameplay output. (a) when meet a life potion; (b) when meet another warrior

6 Report

Your simple report should answer the following questions within TWO A4 pages.

1. Providing example code and necessary elaborations for demonstrating advantages of Dynamic

Typing as specified in Task 2.

2. Using codes for Task 3, give two scenarios in which the Python implementation is better

than the Java implementation. Given the reasons.

3. Using codes for Task 4, illustrate further advantages of Dynamic Typing and Duck Typing.

7 Submission Guidelines

Please read the guidelines CAREFULLY. If you fail to meet the deadline because of submission

problem on your side, marks will still be deducted. So please start your work early!

1. Your submissions will be accepted latest by 11:59 p.m. on Mar 13, but submissions made

after the original deadline would be considered as LATE submissions and penalties will be

imposed in the following manner:

Late submissions before 11:59 p.m. on Mar 12: marks will be deducted by 20%

Late submissions before 11:59 p.m. on Mar 13: marks will be deducted by 50%

2. In the following, SUPPOSE

8

your name is Chan Tai Man,

your student ID is 1155234567,

your username is tmchan, and

your email address is tmchan@cse.cuhk.edu.hk.

3. In your source files, insert the following header. REMEMBER to insert the header according

to the comment rule of Python.

/

CSCI3180 Principles of Programming Languages

--- Declaration ---

I declare that the assignment here submitted is original except for source

material explicitly acknowledged. I also acknowledge that I am aware of

University policy and regulations on honesty in academic work, and of the

disciplinary guidelines and procedures applicable to breaches of such policy

and regulations, as contained in the website

http://www.cuhk.edu.hk/policy/academichonesty/

Assignment 2

Name : Chan Tai Man

Student ID : 1155234567

Email Addr : tmchan@cse.cuhk.edu.hk/

The sample file header is available at

http://course.cse.cuhk.edu.hk/~csci3180/resource/header.txt

4. Task 2 report and the final report should be merged into one report file and submitted to

VeriGuide, which will generate a submission receipt. The report should be named “report.pdf”.

The VeriGuide receipt of report should be named “receipt.pdf”. The report and

receipt should be submitted together with codes in the same ZIP archive.

5. Tar your source files to username.tar by

tar cvf tmchan.tar Othello.py task3 python.zip task4 java.zip \

task4 python.zip report.pdf receipt.pdf

6. Gzip the tarred file to username.tar.gz by

gzip tmchan.tar

7. Uuencode the gzipped file and send it to the course account with the email title “HW2

studentID yourName” by

uuencode tmchan.tar.gz tmchan.tar.gz \

| mailx -s "HW2 1155234567 Chan Tai Man" csci3180@cse.cuhk.edu.hk

8. Please submit your assignment using your Unix accounts.

9. An acknowledgement email will be sent to you if your assignment is received. DO NOT

delete or modify the acknowledgement email. You should contact your TAs for help if you do

not receive the acknowledgement email within 5 minutes after your submission. DO NOT

re-submit just because you do not receive the acknowledgement email.

10. You can check your submission status at

http://course.cse.cuhk.edu.hk/~csci3180/submit/hw2.html.

11. You can re-submit your assignment, but we will only grade the latest submission.

12. Enjoy your work :>

因为专业，所以值得信赖。如有需要，请加QQ：99515681 或邮箱： 

微信：codinghelp