Peg Solitaire

# Peg Solitaire by Al Sweigart al@inventwithpython.com

# More info at https://en.wikipedia.org/wiki/Peg_solitaire

EMPTY = '.'
MARBLE = 'O'
NORTH = 'north'
SOUTH = 'south'
EAST = 'east'
WEST = 'west'
ALL_SPACES = 'C1 D1 E1 C2 D2 E2 A3 B3 C3 D3 E3 F3 G3 A4 B4 C4 D4 E4 F4 G4 A5 B5 C5 D5 E5 F5 G5 C6 D6 E6 C7 D7 E7'.split()

def getNewBoard():
    board = {}
    # Set every space on the board to a marble:
    for space in ALL_SPACES:
        board[space] = MARBLE
    # Set the center space to be empty:
    board['D4'] = EMPTY
    return board


def displayBoard(board):
    spaces = []
    for space in ALL_SPACES:
        spaces.append(board[space])

    print('''
  ABCDEFG
1   {}{}{}
2   {}{}{}
3 {}{}{}{}{}{}{}
4 {}{}{}{}{}{}{}
5 {}{}{}{}{}{}{}
6   {}{}{}
7   {}{}{}
'''.format(*spaces))


def canMoveInDirection(board, space, direction):
    x, y = space # Split up `space` into the x and y coordinates.

    if direction == NORTH:
        neighborSpace = x + str(int(y) - 1) # E.g. convert y of 3 to '2'
        secondNeighborSpace = x + str(int(y) - 2) # E.g. convert y of 3 to '1'
    elif direction == SOUTH:
        neighborSpace = x + str(int(y) + 1) # E.g. convert y of 3 to '4'
        secondNeighborSpace = x + str(int(y) + 2) # E.g. convert y of 3 to '5'
    elif direction == WEST:
        neighborSpace = chr(ord(x) - 1) + y # E.g. convert 'C' to 'B'
        secondNeighborSpace = chr(ord(x) - 2) + y # E.g. convert 'C' to 'A'
    elif direction == EAST:
        neighborSpace = chr(ord(x) + 1) + y # E.g. convert 'C' to 'D'
        secondNeighborSpace = chr(ord(x) + 2) + y # E.g. convert 'C' to 'E'

    # Check if the neighboring space exists:
    if neighborSpace in ALL_SPACES:
        # Check if there is a marble in the neighboring space:
        if board[neighborSpace] == MARBLE:
            # Check if the neighbor's neighboring space exists:
            if secondNeighborSpace in ALL_SPACES:
                # Check if there is an empty space there:
                if board[secondNeighborSpace] == EMPTY:
                    return True
    return False


def getMoveableMarbles(board):
    moveableMarbles = [] # Contain a list of spaces whose marble can jump.
    for space in ALL_SPACES:
        if board[space] == EMPTY:
            continue # There's no marble here, so it's not a valid move.

        # Determine if the marble at this space can move:
        if canMoveInDirection(board, space, NORTH) or \
           canMoveInDirection(board, space, SOUTH) or \
           canMoveInDirection(board, space, WEST) or \
           canMoveInDirection(board, space, EAST):
            moveableMarbles.append(space)
            continue

    return moveableMarbles


def getPlayerMove(board):
    while True:
        # Ask the player to enter a valid move:
        moveableMarbles = getMoveableMarbles(board)
        print('Enter the marble you want to move:')
        print(' '.join(moveableMarbles))
        space = input().upper()

        if space in moveableMarbles:
            break # If the space has a moveable marble, break out of the loop.