Project 01: Connect 4

Board = create_board()
print Board

[[' ', ' ', ' ', ' ', ' ', ' ', ' '],
 [' ', ' ', ' ', ' ', ' ', ' ', ' '],
 [' ', ' ', ' ', ' ', ' ', ' ', ' '],
 [' ', ' ', ' ', ' ', ' ', ' ', ' '],
 [' ', ' ', ' ', ' ', ' ', ' ', ' '],
 [' ', ' ', ' ', ' ', ' ', ' ', ' ']]

drop_piece(Board, 3, PIECE_ONE)
print_board(Board)

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winner = find_winner(Board)
if winner:
    print 'The winner is {}'.format(winner)

display_html(create_board_svg(Board, 40))

# Imports

from IPython.display import display, HTML, clear_output
import random
import time

# Game Constants

ROWS       = 6
COLUMNS    = 7

PIECE_NONE = ' '
PIECE_ONE  = 'x'
PIECE_TWO  = 'o'

PIECE_COLOR_MAP = {
    PIECE_NONE : 'white',
    PIECE_ONE  : 'black',
    PIECE_TWO  : 'red',
}

DIRECTIONS = (
    (-1, -1), (-1, 0), (-1, 1),
    ( 0, -1),          ( 0, 1),
    ( 1, -1), ( 1, 0), ( 1, 1),
)

# Board Functions

def create_board(rows=ROWS, columns=COLUMNS):
    ''' Creates empty Connect 4 board '''
    board = []

    for row in range(rows):
        board_row = []
        for column in range(columns):
            board_row.append(PIECE_NONE)
        board.append(board_row)

    return board

  # Copy board

  def copy_board(board):
      ''' Return a copy of the board '''
      rows    = len(board)
      columns = len(board[0])
      copied  = create_board(rows, columns)

      for row in range(rows):
          for column in range(columns):
              copied[row][column] = board[row][column]
      return copied

def print_board(board):
    ''' Prints Connect 4 board '''
    for row in board:
        print '|' + '|'.join(row) + '|'

def drop_piece(board, column, piece):
    ''' Attempts to drop specified piece into the board at the
    specified column

    If this succeeds, return True, otherwise return False.
    '''

    for row in reversed(board):
        if row[column] == PIECE_NONE:
            row[column] = piece
            return True

    return False

def find_winner(board, length=4):
    ''' Return whether or not the board has a winner '''

    rows    = len(board)
    columns = len(board[0])

    for row in range(rows):
        for column in range(columns):
            if board[row][column] == PIECE_NONE:
                continue

            if check_piece(board, row, column, length):
                return board[row][column]

    return None

def check_piece(board, row, column, length):
    ''' Return whether or not there is a winning sequence starting from
    this piece
    '''
    rows    = len(board)
    columns = len(board[0])

    for dr, dc in DIRECTIONS:
        found_winner = True

        for i in range(1, length):
            r = row + dr*i
            c = column + dc*i

            if r not in range(rows) or c not in range(columns):
                found_winner = False
                break

            if board[r][c] != board[row][column]:
                found_winner = False
                break

        if found_winner:
            return True

    return False

# HTML/SVG Functions

def display_html(s):
    ''' Display string as HTML '''
    display(HTML(s))

def create_board_svg(board, radius):
    ''' Return SVG string containing graphical representation of board '''

    rows     = len(board)
    columns  = len(board[0])
    diameter = 2*radius

    svg  = '<svg height="{}" width="{}">'.format(rows*diameter, columns*diameter)
    svg += '<rect width="100%" height="100%" fill="blue"/>'

    for row in range(rows):
        for column in range(columns):
            piece = board[row][column]
            color = PIECE_COLOR_MAP[piece]
            cx    = column*diameter + radius
            cy    = row*diameter + radius
            svg += '<circle cx="{}" cy="{}" r="{}" fill="{}"/>'.format(cx, cy, radius*.75, color)

    svg += '</svg>'

    return svg

def HumanPlayer(board, history, players):
    ''' Read move from human player '''
    columns = len(board[0])
    column  = -1

    while column not in range(0, columns):
        column = input('Which column? ')

    return column

def RandomPlayer(board, history, players):
    ''' Randomly select a column '''
    columns = len(board[0])
    return random.randint(0, columns - 1)

# Globals

Players = (PIECE_ONE, PIECE_TWO)
History = []
Board   = create_board()
Radius  = 40
Winner  = None
Tries   = 0

# Game Loop

while not Winner:
    turn = len(History)

    if turn % 2 == 0:
        move = HumanPlayer(Board, History, Players)   # Player One
    else:
        move = RandomPlayer(Board, History, Players)  # Player Two

    if drop_piece(Board, move, Players[turn % 2]):
        Tries = 0
        History.append(move)

    if Tries > 3:
        print 'Player {} is stuck!'.format((turn % 2) + 1)
        break

    clear_output()
    display_html(create_board_svg(Board, Radius))

    time.sleep(1)

    Winner = find_winner(Board)

print 'The Winner is {}'.format(PIECE_COLOR_MAP[Winner])

def BotPlayer(board, history, players):
    '''
    This is your AI bot player.  It is given the following arguments:

        Board:    This is the current board.
        History:  This is the history of the previous moves (columns).
        Players:  This is the list of players.

    Your function must not modify any of these objects.

    After analyzing the inputs, your bot should return the column that
    represents the best possible move.
    '''