Python Board类set_colour方法问题：无法在同一网格更新符号

核心问题 #

你的代码无法累积更新网格的根本原因是：没有将网格状态作为Board实例的持久化属性保存。当前__str__和set_colour方法每次都会重新创建全新的空网格，而非基于已有的状态修改，导致每次操作都是独立的新网格。

具体修改步骤 #

1. 初始化持久化网格属性 #

在__init__方法中创建实例属性self.grid，作为保存网格状态的二维列表，初始化为全空（'E'对应的符号）：

def __init__(self, size=19):
    self.size = size
    assert (2 <= self.size <= 26), "Illegal board size: must be between 2 and 26."
    # 初始化网格：二维列表，每个元素初始为'E'对应的符号
    self.grid = [[self.points['E'] for _ in range(self.size)] for _ in range(self.size)]

2. 重构__str__方法 #

__str__的职责是返回表示当前网格的字符串，而非直接打印。基于self.grid生成字符串，同时处理行号倒序和列名：

def __str__(self):
    column_names = letters[:self.size]
    # 构建头部列名
    header = '   ' + ' '.join(column_names)
    rows = [header]
    # 倒序遍历行号（从size到1）
    for row_num in reversed(range(1, self.size + 1)):
        # 找到对应的网格行：row_num=1对应grid的最后一行，索引为self.size - row_num
        grid_row = self.grid[self.size - row_num]
        # 格式化行号（右对齐2位）+ 行内容
        row_str = f"{row_num:2d} {' '.join(grid_row)}"
        rows.append(row_str)
    # 拼接所有行并返回
    return '\n'.join(rows)

3. 修复set_colour方法 #

移除方法内创建新网格的代码，直接操作self.grid，只负责修改状态，不处理输出：

• 修正坐标解析逻辑，转换为正确的网格索引
• 修复断言条件的错误
• 移除无用的循环、打印和变量

修改后的set_colour：

def set_colour(self, coords, colour_name):
    # 颜色合法性断言
    assert colour_name in self.points, "invalid colour name"
    # 坐标格式断言
    assert 2 <= len(coords) <= 3, "invalid coordinates"
    
    # 解析坐标
    alphabetical_coord = coords[0].upper()  # 统一转为大写，兼容小写输入
    numerical_coord = coords[1:]
    
    # 坐标范围断言
    assert ord(alphabetical_coord) in range(ord('A'), ord('Z')+1), "column out of range"
    assert numerical_coord.isdigit(), "invalid row number"
    row_num = int(numerical_coord)
    assert 1 <= row_num <= self.size, "row out of range"
    
    # 转换为网格索引：列是字母对应的索引，行是size - row_num（因为行号倒序）
    col_idx = ord(alphabetical_coord) - ord('A')
    row_idx = self.size - row_num
    
    # 修改网格对应位置的符号
    self.grid[row_idx][col_idx] = self.points[colour_name]

4. 修正代码缩进和语法错误 #

确保所有方法（get_size、set_colour等）都缩进在Board类内部，移除重复的导入和无用代码。

修正后的完整代码 #

from string import ascii_uppercase as letters

class Board():
    points = {'E': '.', 'B': '@', 'W': 'O'}

    def __init__(self, size=19):
        self.size = size
        assert (2 <= self.size <= 26), "Illegal board size: must be between 2 and 26."
        # 初始化持久化网格
        self.grid = [[self.points['E'] for _ in range(self.size)] for _ in range(self.size)]

    def __str__(self):
        column_names = letters[:self.size]
        header = '   ' + ' '.join(column_names)
        rows = [header]
        for row_num in reversed(range(1, self.size + 1)):
            row_idx = self.size - row_num
            grid_row = self.grid[row_idx]
            row_str = f"{row_num:2d} {' '.join(grid_row)}"
            rows.append(row_str)
        return '\n'.join(rows)

    def get_size(self):
        return self.size

    def set_colour(self, coords, colour_name):
        assert colour_name in self.points, "invalid colour name"
        assert 2 <= len(coords) <= 3, "invalid coordinates"
        
        alphabetical_coord = coords[0].upper()
        numerical_coord = coords[1:]
        
        assert ord(alphabetical_coord) in range(ord('A'), ord('Z')+1), "column out of range"
        assert numerical_coord.isdigit(), "invalid row number"
        row_num = int(numerical_coord)
        assert 1 <= row_num <= self.size, "row out of range"
        
        col_idx = ord(alphabetical_coord) - ord('A')
        row_idx = self.size - row_num
        
        self.grid[row_idx][col_idx] = self.points[colour_name]

# 使用示例
if __name__ == "__main__":
    b = Board(5)
    b.set_colour("B1", "W")
    b.set_colour("C1", "B")
    b.set_colour("D1", "B")
    print(b)

验证输出 #

运行上述代码后，会得到预期的累积更新结果：

A B C D E
 5 . . . . .
 4 . . . . .
 3 . . . . .
 2 . . . . .
 1 . O @ @ .

内容的提问来源于stack exchange，提问作者Anne_Music