为什么我的新手代码会额外增加？

Question

这里是新的Python程序员，拥有相当丰富的c#经验。我试图用Python自动完成这个练习：

Chess Dictionary Validator In this chapter, we used the dictionary value {'1h': 'bking', '6c': 'wqueen', '2g': 'bbishop', '5h': 'bqueen', '3e': 'wking'} to represent a chess board. Write a function named isValidChessBoard() that takes a dictionary argument and returns True or False depending on if the board is valid. A valid board will have exactly one black king and exactly one white king. Each player can only have at most 16 pieces, at most 8 pawns, and all pieces must be on a valid space from '1a' to '8h'; that is, a piece can’t be on space '9z'. The piece names begin with either a 'w' or 'b' to represent white or black, followed by 'pawn', 'knight', 'bishop', 'rook', 'queen', or 'king'. This function should detect when a bug has resulted in an improper chess board.

我目前的解决办法如下：

testBoard00 = {'1h': 'bking', '6c': 'wqueen', '2g': 'bbishop', '5h': 'bqueen', '3e': 'wking'}

testBoard01 = {'1a': 'brook', '1b': 'bknight', '1c': 'bbishop', '1d': 'bqueen', '1e': 'bking', '1f' : 'bbishop', '1g' : 'bknight', '1h' : 'brook',
               '2a': 'bpawn', '2b' : 'bpawn', '2c': 'bpawn', '2d' : 'bpawn', '2e': 'bpawn', '2f' : 'bpawn', '2g': 'bpawn', '2h' : 'bpawn',
               '8a': 'wrook', '8b': 'wknight', '8c': 'wbishop', '8d': 'wqueen', '8e': 'wking', '8f' : 'wbishop', '8g' : 'wknight', '8h' : 'wrook',
               '7a': 'bpawn', '7b' : 'bpawn', '7c': 'bpawn', '7d' : 'bpawn', '7e': 'bpawn', '7f' : 'bpawn', '7g': 'bpawn', '7h' : 'bpawn',}

testBoard02 = {'1a': 'brook', '1b': 'bknight', '1c': 'bbishop', '1d': 'bqueen', '1e': 'bking', '1f' : 'bbishop', '1g' : 'bknight', '1h' : 'brook',
               '2a': 'bpawn', '2b' : 'bpawn', '2c': 'bpawn', '2d' : 'bpawn', '2e': 'bpawn', '2f' : 'bpawn', '2g': 'bpawn', '2h' : 'bpawn',
               '8a': 'wrook', '8b': 'wknight', '8c': 'wbishop', '8d': 'wqueen', '8e': 'wking', '8f' : 'wbishop', '8g' : 'bpawn', '8h' : 'wrook', # Extra pawn instead of second Knight!
               '7a': 'wpawn', '7b' : 'wpawn', '7c': 'wpawn', '7d' : 'wpawn', '7e': 'wpawn', '7f' : 'wpawn', '7g': 'wpawn', '7h' : 'wpawn',}

testBoard03 = {'1a': 'brook', '1b': 'bknight', '1c': 'bbishop', '1d': 'bqueen', '1e': 'bking', '1f' : 'bbishop', '1g' : 'bknight', '1h' : 'brook',
               '2a': 'bpawn', '2b' : 'bpawn', '2c': 'bpawn', '2d' : 'bpawn', '2e': 'bpawn', '2f' : 'bpawn', '2g': 'bpawn', '2h' : 'bpawn',
               '8a': 'wrook', '8b': 'wknight', '8c': 'wbishop', '8d': 'wqueen', '8f' : 'wbishop', '8g' : 'wknight', '8h' : 'wrook', # Missing a king!
               '7a': 'wpawn', '7b' : 'wpawn', '7c': 'wpawn', '7d' : 'wpawn', '7e': 'wpawn', '7f' : 'wpawn', '7g': 'wpawn', '7h' : 'wpawn',}

letters = 'abcdefgh'
numbers = '12345678'

BOARDUNITS = { 'pawn' : 0, 'rook' : 0, 'knight' : 0, 'bishop' : 0, 'queen' : 0, 'king' : 0 }
TOTALUNITS = { 'pawn' : 16, 'rook' : 4, 'knight' : 4, 'bishop' : 4, 'queen' : 2, 'king' : 2 }

def isValidChessBoard(board):

    boardIsValid = True

    for k in board:
        let = str(k[1:]).lower()
        num = str(k[:1]).lower()

        if let not in letters:
            print('INVALID: Letter is not in acceptable range!')
            boardIsValid = false
            return boardIsValid

        if num not in numbers:
            print('INVALID: Numbers are not in acceptable range!')
            boardIsValid = false
            return boardIsValid

        # print('Number is ' + num + ' and Letter is ' + let + '.')

    wPieces = bPieces = BOARDUNITS

    for k in board:
        # print('K is now: ' + str(k) + ' which is equal to ' + board[k])
        #piece = board[k]

        print(str(wPieces['king']) + ' white King(s), ' + str(bPieces['king']) + ' black King(s)')

        if board[k][0] == 'b':
            #print('First character of piece is ' + piece[0])

            if(board[k][1:] in bPieces):
                if(board[k][1:] == 'king'):
                    print('Black king here!')
                #print('[][] Black ' + piece[1:] + ' is in bPieces!')
                print('Before Increment: ' + str(wPieces['king']) + ' white King(s), ' + str(bPieces['king']) + ' black King(s)')
                bPieces[board[k][1:]] += 1
                print('After Increment: ' + str(wPieces['king']) + ' white King(s), ' + str(bPieces['king']) + ' black King(s)')
            #else:
            #   print('#### ' + piece[1] + ' is not found in bPieces.')

        elif board[k][0] == 'w':
            #print('First character of piece is ' + piece[0])

            if(board[k][1:] in wPieces):
                if(board[k][1:] == 'king'):
                    print('White king here!')
                print('[][] White '+ board[k][1:] + ' is in wPieces!')
                wPieces[board[k][1:]] += 1
            else:
                print('#### ' + board[k][1] + ' is not found in wPieces.')
        else:
            print('Playing piece is missing "black" or "white" characteristic.')
            return False


        for k in bPieces:
            #print('We have ' + str(bPieces[k]) + ' Black ' + str(k) + '(s)')
            #print('We have ' + str(wPieces[k]) + ' White ' + str(k) + '(s)')
            if bPieces[k] > TOTALUNITS[k] or wPieces[k] > TOTALUNITS[k]:

                print('INVALID: Too many pieces!')

                boardIsValid = False
    print(str(wPieces['king']) + ' white King(s), ' + str(bPieces['king']) + ' black King(s)')
    if bPieces['king'] <= 0 or wPieces['king'] <= 0:
        print('INVALID: One of our kings is missing.')
        #print('Black kings number: ' + str(bPieces['king']))
        #print('White kings number: ' + str(wPieces['king']))
        boardIsValid = False    

    return boardIsValid

if isValidChessBoard(testBoard03):
    print("Board is valid!")
else:
    print("Board is invalid.")

第60行后，在下面的代码中间看到…

print('Before Increment: ' + str(wPieces['king']) + ' white King(s), ' + str(bPieces['king']) + ' black King(s)')
                bPieces[board[k][1:]] += 1
                print('After Increment: ' + str(wPieces['king']) + ' white King(s), ' + str(bPieces['king']) + ' black King(s)')

…我得到了黑国王的预期增量，但我也得到了白国王的增量。我很困惑。这里是否缺少某种全局变量，或者我只是在编写乱七八糟的代码

我真的很想在这双眼睛上多看一眼。提前谢谢你，牧师

Answer 1

错误出现在以下行中：

wPieces = bPieces = BOARDUNITS

此语句的目的是创建BOARDUNITS字典的两个铜片。相反，此行将wPieces和bPieces变量分配给对同一字典对象的引用。因此，修改wPieces的条目也会修改bPieces，也会修改BOARDUNITS，因为所有三个标识符都指向同一个对象

您可以创建BOARDUNITS对象的副本，如下所示：

wPieces = BOARDUNITS.copy()
bPieces = BOARDUNITS.copy()