to_strings函数的输入是网格，因此网格显示的任何内容都应转换为字符串列表，其中输入示例：

A B C
 1 . . .
 2 . @ .
 3 . O .

输出示例：

['...', '.@.', '.O.']
True

第一个问题是该特定功能，因为它没有提供预期输出

def to_strings(self):
        from itertools import chain

        m_list_tostring=[]
        for i in range(len(self.grid)):
            x=list(chain.from_iterable(self.grid))
            m_list_tostring = ''.join([str(x) for self.grid, i in enumerate(x)])  # to convert the list of characters into a string
        print(x)

    return str(x)

我还遇到了一个特定Assert错误的问题，需要在检查无效输入（字母x应指示无效行的行坐标）时引发该错误，其中“invalid character in row x”，下面显示的代码是我想到的，但它给出了错误

assert i == self.grid[i], "invalid character in row "+i

我需要在构造函数中添加一个额外的可选参数from_strings，如果它存在，这个参数必须是一个字符串列表，其中每个字符串给出棋盘的一行，使用__str__()方法中使用的字符编码，但没有空格和坐标字母。
还有一个方法to_strings(self)，它将电路板表示为字符串列表，格式与__init__()方法从from_strings接受的格式相同。
我怎样才能得到预期的输出？

from string import ascii_uppercase as letters
class Board:
#Dictionary created for the colours and the respected symbols
    points = {'E': '.', 'B': '@', 'W': 'O'}
#Constructor
    def __init__(self,size=19,from_strings=None):
        assert 2 <= size <= 26, "Illegal board size: must be between 2 and 26."
        assert type(from_strings) is list,"input is not a list"
        assert len(from_strings)==size, "length of input list does not match size"
        for i in from_strings:
            assert type(i)==str, "row "+i+" is not a string"
            assert len(i)==size,"length of row "+i+" does not match size"
            #assert i== b[i], "invalid character in row "+i
        self.size = size
        self.grid = [['E'] * size for _ in range(size)]
        self.from_strings = [] if from_strings is None else from_strings
       def get_size(self): #Returns the size of the grid created by the constructor
        return self.size

    def __str__(self): #creating the grid
        padding=' ' #Creating a variable with a space assigned so that it acts as a padding to the rows that have a single digit
        heading = '   ' + ' '.join(letters[:self.size]) #Alphabetical heading is created
        lines = [heading] #adding the alphabetical heading into a list named lines to which the rows will be added later
        for r, row in enumerate(self.grid):
            if len(self.grid)<10: #for the grid with a size less than 10 to add the space to the start of the row for the single digits to be aligned
                line = " " +f'{self.size - r} ' + ' '.join(self.points[x] for x in row)
                lines.append(line)
            else: #for the grids that are larger than 9
                if r>9: #for rows 1 to 9 the single digits are aligned according to the first digit from the right of the two digit rows
                    line =f'{self.size - r} ' + ' '.join(self.points[x] for x in row)
                    line=padding+line #adding the space using the variable padding to the row created
                    lines.append(line) #adding the row to the list of rows
                else: #for the rows 10 onwards - as there is no requirement to add a padding it is not added here
                    line = f'{self.size - r} ' + ' '.join(self.points[x] for x in row)#creation of the row
                    lines.append(line) #adding the newly created row to the list of rows
        return '\n'.join(lines)

    def _to_row_and_column(self, coords):
        # destructure coordinates like "B2" to "B" and 2
        alpha, num = coords
        colnum = ord(alpha) - ord('A') + 1
        rownum = self.size - int(num) + 1
        assert 1 <= rownum <= self.size,"row out of range"
        assert 1 <= colnum <= self.size,'column out of range'
        return rownum, colnum

    def set_colour(self, coords, colour_name):
        rownum, colnum = self._to_row_and_column(coords)
        assert len(coords)==2 or len(coords)==3, "invalid coordinates"
        assert colour_name in self.points,"invalid colour name"
        self.grid[rownum - 1][colnum - 1] = colour_name

    def get_colour(self, coords):
        rownum, colnum = self._to_row_and_column(coords)
        return self.grid[rownum - 1][colnum - 1]

    def to_strings(self):
        from itertools import chain
        m_list_tostring=[]
        for i in range(len(self.grid)):
            x=list(chain.from_iterable(self.grid))
            m_list_tostring = ''.join([str(x) for self.grid, i in enumerate(x)])  # to convert the list of characters into a string
            print(x)
        
        return x

b =Board(3, ["O.O", ".@.", "@O."])
print(b)
print(b.to_strings())
c =Board(b.get_size(), b.to_strings())
print(str(b) == str(c))

现在我的代码是这样的
但是，我没有得到预期的输出，如下所示

A B C
 3 O . O
 2 . @ .
 1 @ O .

['O.O', '.@.', '@O.']
True

我得到的代码输出是：

['E', 'E', 'E', 'E', 'E', 'E', 'E', 'W', 'E']