Python 元组超出范围

Question

我一直收到错误 IndexError: tuple out of range 我希望你们能帮助我完成我的程序

MIN_ROW = 0
MAX_ROW = 3
MIN_COLUMN = 0
MAX_COLUMN = 19

问题似乎仍然存在于第 7 行

def display(theMap):
r = 0
c = 0
print("PLAYER MAP")
for r in range (0, (MAX_ROW + 1), 1):
    for c in range (0, (MAX_COLUMN + 1), 1):
        print(theMap[r][c])   #this line
    print()
print()

def loadMap():
theMap = []
for r in range(0,(MAX_ROW+1), 1):
    theMap.append([])
    for c in range(0,(MAX_COLUMN+1), 1):
        theMap[r].append(" ")
#           0    1    2    3    4    5    6    7    8    9   10   11    12   13   14   15   16    17   18   19 
map  [0] =   "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J"
map  [1] =   "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-"
map  [2] =   "|r|","| |", "| |", "| |", "| |", "| |", "| |", "| |", "| |", "| |", "|" 
map  [3] =   "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-"
return theMap

所以我不确定我的元组是如何超出范围的，但希望你们能指出并帮助我

Answer 1

用显式循环编写东西通常会导致难以调试的问题。这就是 Python 不强制您这样做的原因，实际上鼓励您不要这样做:

def display(theMap):
    print("PLAYER MAP")
    for row in theMap:
        for col in row:
            print(col)
        print()
    print()

这仍然不是您真正想要的，因为 print(col) 打印换行符。您不希望每个单元格都在自己的行上，您希望单元格之间有空格，并且每一行都在自己的行上。为此，您必须改为 print(col, end=' ')。

或者，更简单地说:

def display(theMap):
    print("PLAYER MAP")
    for row in theMap:
        print(' '.join(row))
    print()

或者，更简洁——但可能不那么简单:

def display(theMap):
    print("PLAYER MAP")
    print('\n'.join(' '.join(row) for row in theMap))
    print()

您可以通过一次创建 theMap 来类似地改进 theMap，而不是创建空行，然后替换它们。例如:

def loadMap():
    return [
        ("0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J"),
        ("-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-"),
        ("|r|","| |", "| |", "| |", "| |", "| |", "| |", "| |", "| |", "| |", "|"),
        ("-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-")]

一般来说，每当您发现自己在 Python 中编写 for i in range(something) 时，您就在做一些不必要的事情，您最终只会调试。

现在，您可能会争辩说这种样式不会“捕获错误”。但是用显式循环做事只能捕获少数错误，并且以一种很难调试的方式捕获它们。如果你知道你的先决条件，你通常可以更简单明了地写它们:

theMap = loadMap()
assert(all(len(row) == len(theMap[0]) for row in theMap))

此外，如果您知道测试用例的输出应该是什么，则可以编写单元测试来验证输出。

无论如何，即使解决了所有这些问题，您仍然会遇到一些问题。例如，除了第 2 行比其他行短几列之外，该行中的各个列是其他行中的 3 倍大，因此它根本不会排成一行。但是一旦你让它运行起来，调试视觉内容应该会更容易。

退后一步，您显然要将“r”推进到第 2 行。事实上，您可能需要表示 map 的只是宽度和当前位置:

def display(mapWidth, playerPosition):
    print('PLAYER MAP')
    # Display the first line. This is the header, with a label for each of the
    # mapWidth columsn, with a space between each label, and an extra space at
    # the start, like ' 0 1 2 3 4'. The ' '.join(s) creates a new string by 
    # putting a space between each element of s. The '012...XYZ'[:mapWidth] 
    # just takes the first mapWidth characters of the longer string. 
    print(' ' + ' '.join('0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'[:mapWidth]))

    # Display the second line. This is just a '-' for each column, with a space
    # between each, and an extra space at the start, like ' - - - - -'. The join
    # works the same as above; the '-' * mapWidth creates a string with mapWidth
    # copies of '-'.
    print(' ' + ' '.join('-' * mapWidth))

    # Display the third line. This is the trickiest. This is cell for each column,
    # where the first playerPosition cells are '| |', the playerPositionth is 
    # '|r|', and the rest are again '| |', with no space between them. It seemed
    # simpler to treat this as a group of playerPosition+1 '|' characters with 
    # spaces between, an 'r' character, and a group of mapWidth-playerPosition
    # '|' characters with spaces between again, but there are various different 
    # ways of printing something equivalent. The only new thing here is the 
    # end='' keyword argument--without that, each print ends with a newline.
    print(' '.join('|' * (playerPosition + 1)), end='')
    print('r', end='')
    print(' '.join('|' * (mapWidth - playerPosition)))

    # Fourth line, same as the second.
    print(' ' + ' '.join('-' * mapWidth))
    print()

根据您对 join 方法、print 函数等的熟悉程度，您可能会发现这更容易阅读:

def display(mapWidth, playerPosition):
    print('PLAYER MAP')
    print(' ' + ' '.join('0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'[:mapWidth]))
    print(' -' * mapWidth)
    print(' '.join('|' * (playerPosition + 1)) +
          'r' +
          ' '.join('|' * (mapWidth - playerPosition)))
    print(' -' * mapWidth)
    print()

值得思考为什么，例如，' ' + ' '.join('-' * 8) 与 ' -' * 8 是同一回事。

还有另一种实现棘手的第三行的方法是:

   # Print mapWidth '|' characters, each followed by a ' ', except for the one
   # at the player position, which is followed by an 'r'. Then we still need one
   # more '|' at the end.
   print(''.join('|' + (' ' if i != playerPosition else 'r') 
                 for i in range(mapWidth) + '|')

我认为这是最容易用英语解释的，但是将其翻译成 Python 需要生成器表达式和三元 if 表达式，您可能还不想学习这两者——最终结果甚至是Python 开发人员可能不想阅读的经验。

当然，当有疑问时，您总是可以将内容拉出到单独的行中，甚至是单独的函数中，以使其更具可读性:

    cellsBeforePlayer = '| ' * playerPosition
    cellsWithPlayer = cellsBeforePlayer + '|r|'
    cellsToEnd = cellsWithPlayer + '| ' * (mapWidth - playerPosition)
    print(cellsToEnd)

无论如何，这些都做同样的事情:

>>> display(MAX_COLUMN - MIN_COLUMN + 1, 3)
PLAYER MAP
 0 1 2 3 4 5 6 7 8 9 A B C D E F G H I J
 - - - - - - - - - - - - - - - - - - - -
| | | |r| | | | | | | | | | | | | | | | |
 - - - - - - - - - - - - - - - - - - - -

除非那些 MIN_COLUMN 和 MAX_COLUMN 值是要求的一部分，否则我将使用单个 COLUMNS=20 变量来代替——同样，它避免了另一种常见的差一错误(函数调用中的 + 1，很容易在需要时忘记包含，或者在不需要时添加错误)。

或者，如果 map 宽度固定，那就更简单了:

def display(playerPosition):
    print('PLAYER MAP')
    print(' ' + ' '.join('0123456789ABCDEFGHIJ'))
    print(' -' * 20)
    print(' '.join('|' * (playerPosition + 1)) +
          'r' +
          ' '.join('|' * (20 - playerPosition)))
    print(' -' * 20)
    print()

无论如何，这样做的优势超出了显示的简单性，而且根本不需要loadMap——来移动播放器，而不是这样:

theMap[2][playerPosition] = '| |'
playerPosition += stepsMoved
theMap[2][playerPosition] = '|r|'
display(theMap)

你只需这样做:

playerPosition += stepsMoved
display(playerPosition)

您的整个游戏状态从一个复杂的列表列表减少到一个整数。