EECS 110 Lec 15 Classes and Objects 2

EECS 110: Lec 15: Classes and Objects (2) Aleksandar Kuzmanovic Northwestern University http: //cs. northwestern. edu/~akuzma/classes/EECS 110 -s 10/

EECS 110 important dates Projects Fri. , 5/21: online Mon. , 5/24: class Projects Fri. , 5/28: recitation (LR 5) Tue. , 6/1: recitation, W. lab Final! Wed. , 5/26: rev. for final Wed. , 6/2, final

Classes & Objects An object-oriented programming language allows you to build your own customized types of variables. (1) A class is a type of variable. (2) An object is one such variable. There will typically be MANY objects of a single class.

Objects An object is a data structure (like a list), except (1) Its data elements have names chosen by the programmer. (2) Data elements are chosen & organized by the programmer (3) An object can have behaviors built-in by the programmer.

Objects An object is a data structure (like a list), except (1) Its data elements have names chosen by the programmer. (2) Data elements are chosen & organized by the programmer (3) An object can have behaviors built-in by the programmer. usually called "methods" instead of functions

class Date: """ a blueprint (class) for objects that represent calendar days """ def __init__( self, mo, dy, yr ): """ the Date constructor """ self. month = mo self. day = dy self. year = yr The Date class def __repr__( self ): """ used for printing Dates """ s = "%02 d/%04 d" % (self. month, self. day, self. year) return s

EECS 110 Today Connect Four X to move. Is there a way to win? | | | | | | |X| | | |X|O|O|O|X|O| | -------0 1 2 3 4 5 6

Aargh! Python has no Connect-four datatype… | | | | | | |X| | | |X|O|O|O|X| |O| -------0 1 2 3 4 5 6 … but we can correct that!

Designing classes 1) What data? (Data Members) Not limited to 7 x 6! 2) What are objects' crucial capabilities? (Methods)

Designing classes 1) What data? (Data Members) - height, width - Where the chips are - Whose turn it is - Winning condition - End condition (number of chips played) 2) What are objects' crucial capabilities? (Methods) Not limited to 7 x 6!

Designing classes 1) What data? (Data Members) - height, width - Where the chips are - Whose turn it is - Winning condition - End condition (number of chips played) 2) What are objects' crucial capabilities? (Methods) - creates a new object - check for win - print - get the next move/switch turn -check for full board Not limited to 7 x 6!

Connect Four: Board b list data the object b str str str int width int height data What is the name of the method that will construct this data?

Connect Four: Board b list data the object b str str str int width int height data What is the name of the method that will construct this data? __init__(…)

Connect Four: constructor class Board: """ a datatype representing a C 4 board with an arbitrary number of rows and cols """ def __init__( self, width, height ): """ the constructor for objects of type Board """ self. width = width self. height = height self. data = [] # this will be the board for row in range( height ): # 6 board. Row = [] for col in range( width ): # 7 board. Row += [' '] # add a space to this row self. data += [board. Row]

Connect Four: Board b list data str str str What is the name of the method that will print this data? the object b str str | | | | | | |X| | | |X|O|O|O|X| |O| -------0 1 2 3 4 5 6 int width int height

Connect Four: __repr__ def __repr__(self): """ this method returns a string representation for an object of type Board """ s = '' which row is row 0, for row in range( self. height ): row 1, and so on? s += '|' for col in range( self. width ): s += self. data[row][col] + '|' s += 'n' To remove? To add? return s

Connect Four: __repr__ def __repr__(self): """ this method returns a string representation for an object of type Board """ s = '' which row is row 0, for row in range( self. height ): row 1, and so on? s += '|' for col in range( self. width ): s += self. data[row][col] + '|' s += 'n‘ s += '--'*self. width + '-n‘ for col in range( self. width ): s += ' ' + str(col%10) s += 'n' return s

class Board { a C 4 board col # 'X' or 'O' def mystery(self, col, ox): for row in range( self. height ): if self. data[row][col] != ' ': self. data[row-1][col] = ox self. data[self. height-1][col] = ox "Quiz" Step through this mystery method. What is each line doing? What's going wrong? def allows. Move(self, col): Write allows. Move to return True if col is a valid move; False otherwise. }

class Board { a C 4 board col # 'X' or 'O' def mystery(self, col, ox): for row in range( self. height ): if self. data[row][col] != ' ': self. data[row-1][col] = ox self. data[self. height-1][col] = ox "Quiz" Step through this mystery method. What is each line doing? What's going wrong? # Adds ox at the top of a column # But at the same time overwrites the existing # elements in the column… # Does not check if it is possible to write in a column… def allows. Move(self, col): Write allows. Move to return True if col is a valid move; False otherwise. }

class Board { a C 4 board col # 'X' or 'O' def mystery 1(self, col, ox): if allows. Move(col): for row in range( self. height ): if self. data[row][col] != ' ': self. data[row-1][col] = ox return self. data[self. height-1][col] = ox "Quiz" Step through this mystery method. What is each line doing? What's going wrong? def allows. Move(self, col): Write allows. Move to return True if col is a valid move; False otherwise. }

class Board { a C 4 board col # 'X' or 'O' def mystery 1(self, col, ox): if allows. Move(col): for row in range( self. height ): if self. data[row][col] != ' ': self. data[row-1][col] = ox return self. data[self. height-1][col] = ox "Quiz" Step through this mystery method. What is each line doing? What's going wrong? def allows. Move(self, col): if 0 <= col < self. width: return self. data[0][col] == ' ' Write allows. Move to return True if col is a valid move; False otherwise. }

C 4 Board class: methods the “constructor” __init__( self, width, height ) checks if allowed allows. Move( self, col ) places a checker removes a checker outputs a string checks if any space is left checks if a player has won play! add. Move( self, col, ox ) del. Move( self, col ) __repr__( self ) is. Full( self ) wins. For( self, ox ) host. Game( self ) Which of these will require the most thought?

wins. For( self, ox ) b. wins. For( 'X' ) b or 'O' X O Thoughts?

wins. For( self, ox ) b def wins. For(self, ox): # check for horizontal wins for row in range(0, self. height): for col in range(0, self. width-3): if self. data[row][col] == ox and self. data[row][col+1] == ox and self. data[row][col+2] == ox and self. data[row][col+3] == ox: return True X O # check for vertical wins Thoughts?

The Player class (Extra credit) Details Player p. For. X (data and methods) What data and methods are needed to construct and implement a Player object?

Player Picture of a Player object DATA Player p. For. X 3 'LEFT' 'X' string ox string tbt checker, O or X tiebreak. Type int ply __init__(self, ox, tbt, ply) __repr__(self) opp. Ch(self) score. Board(self, b) scores. For(self, b) tiebreak. Move(self, scores) next. Move(self, b) METHODS

score. Board ‘X’ ‘O’ Assigns a score to any board, b A simple system: Score for 100. 0 50. 0 for a win for anything else for a loss Score for

score. Board ‘X’ ‘O’ Assigns a score to any board, b A simple system: Score for 100. 0 50. 0 for a win for anything else for a loss Score for

score. Board ‘X’ ‘O’ Assigns a score to any board, b A simple system: Score for 100. 0 50. 0 for a win for anything else for a loss Score for 50. 0

score. Board Assigns a score to any board, b A simple system: 100. 0 50. 0 for a win for anything else for a loss Implementation ideas… score. Board(self, b) How can there be no 'X' or 'O' input? What class is this method in? What methods that already exist will come in handy? This doesn't seem to be looking very far ahead !

Looking further ahead… score. Board looks ahead 0 moves 0 -ply If you look one move ahead, how many possibilities are there to consider? A 1 -ply lookahead player will "see" an impending victory. to move… 1 -ply score

Looking further ahead… score. Board looks ahead 0 moves 0 -ply If you look one move ahead, how many possibilities are there to consider? A 1 -ply lookahead player will "see" an impending victory. to move… 1 -ply -1 50 50 50 100 50 50 score

Looking further ahead… score. Board looks ahead 0 moves 0 -ply If you look one move ahead, how many possibilities are there to consider? A 2 -ply lookahead player will also "see" an opponent's impending victory. to move… -1 0 0 0 50 0 0 2 -ply score

Looking further ahead… score. Board looks ahead 0 moves 0 -ply If you look one move ahead, how many possibilities are there to consider? 1 -ply 2 -ply scores. For( self, b ) returns a LIST of scores, one for each column you can choose to move next…

Example 1 -ply and 2 -ply lookahead scores |O| | | | |X| | | |O| |X| |O| | | |X|O|X| | | |O|O|X| |X| |X|O|O| |X| |O|O|O|X|X| -------0 1 2 3 4 5 6 It is O’s move. What scores does a 1 -ply lookahead for O assign to each move? col 0 col 1 col 2 col 3 col 4 col 5 col 6 Which change at 2 -ply?

Example 1 -ply and 2 -ply lookahead scores |O| | | | |X| | | |O| |X| |O| | | |X|O|X| | | |O|O|X| |X| |X|O|O| |X| |O|O|O|X|X| -------0 1 2 3 4 5 6 It is O’s move. What scores does a 1 -ply lookahead for O assign to each move? col 0 col 1 col 2 col 3 col 4 col 5 col 6 -1 100 50 Which change at 2 -ply?

Example 1 -ply and 2 -ply lookahead scores |O| | | | |X| | | |O| |X| |O| | | |X|O|X| | | |O|O|X| |X| |X|O|O| |X| |O|O|O|X|X| -------0 1 2 3 4 5 6 It is O’s move. What scores does a 1 -ply lookahead for O assign to each move? col 0 col 1 col 2 col 3 col 4 col 5 col 6 -1 100 50 50 50 100 50 col 1 col 2 col 3 col 4 col 5 col 6 -1 100 0 100 50 1 -ply 2 -ply

Example 1 -ply and 2 -ply lookahead scores | | | |O| | | | |X| |X|O| |X|O|O|X| |X|O|O|O| |O|X| -------0 1 2 3 4 5 6 It is X’s move. What scores does a 2 -ply lookahead for X assign to each move? col 0 col 1 col 2 col 3 col 4 col 5 col 6

Example 1 -ply and 2 -ply lookahead scores | | | |O| | | | |X| |X|O| |X|O|O|X| |X|O|O|O| |O|X| -------0 1 2 3 4 5 6 It is X’s move. What scores does a 2 -ply lookahead for X assign to each move? col 0 col 1 col 2 col 3 col 4 col 5 col 6 100 0 50 0 -1

Practice b ‘X’ ‘O’ col 0 col 1 col 2 col 3 col 4 col 5 col 6 0 -ply scores for O: 1 -ply scores for O: 2 -ply scores for O: 3 -ply scores for O:

Solutions 0 -ply scores for O: 1 -ply scores for O: 2 -ply scores for O: 3 -ply scores for O: b ‘X’ ‘O’ col 0 col 1 col 2 col 3 col 4 col 5 col 6 -1 50 50 50 col 1 col 2 col 3 col 4 col 5 col 6 -1 50 50 100 50 50 50 col 1 col 2 col 3 col 4 col 5 col 6 -1 0 0 100