Learn Classes and Objects by Building a Sudoku Solver - Step 19

Next, you will create a string representation of the row with spaces between each element.
For that, outside the innermost for loop body, create a string row. Assign the following formatted string f'║ {" ".join(row_list)} ║\n' to it to join the elements of row_list with a space in between.

create a string row

Isn’t row a variable?

Your code so far

class Board:
    def __init__(self, board):
        self.board = board

    def __str__(self):
        upper_lines = f'\n╔═══{"╤═══"*2}{"╦═══"}{"╤═══"*2}{"╦═══"}{"╤═══"*2}╗\n'
        middle_lines = f'╟───{"┼───"*2}{"╫───"}{"┼───"*2}{"╫───"}{"┼───"*2}╢\n'
        lower_lines = f'╚═══{"╧═══"*2}{"╩═══"}{"╧═══"*2}{"╩═══"}{"╧═══"*2}╝\n'
        board_string = upper_lines

        for index, line in enumerate(self.board):
            row_list = []

# User Editable Region

            for square_no, part in enumerate([line[:3], line[3:6], line[6:]], start=1):
                row_square = '|'.join(str(item) for item in part)
                if square_no != 3:

# User Editable Region

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Challenge Information:

Learn Classes and Objects by Building a Sudoku Solver - Step 19

Welcome to the forum @Mazi

Here is the error message:

Assign the formatted string f'║ {" ".join(row_list)} ║\n' to a variable named row.

The variable you are asked to declare is row.
The variable is assigned the value of the formatted string.

Happy coding