Python 中的数独 GUI 与 Tkinter - StringVar 未更新

Question

I recently successfully wrote a recursive code that uses backtracking to solve a simple sudoku puzzle. I want to create it so that I solved the puzzle live, ie with the numbers changing in real-time and wanted to do so using the tkinter module. I created a 9*9 board with each number as a particular label and stored the text of the label in a StringVar() so I could update it continuously. All the StringVars were stored in a 9*9 array(called textvars) so that they corresponded to the original sudoku board I wanted to solve, and I could thus use the row and column number to update the text. The following is the code for this part:

def main():
    textvars = []
    t1 = []
    board = [[3, 0, 6, 5, 0, 8, 4, 0, 0],
             [5, 2, 0, 0, 0, 0, 0, 0, 0],
             [0, 8, 7, 0, 0, 0, 0, 3, 1],
             [0, 0, 3, 0, 1, 0, 0, 8, 0],
             [9, 0, 0, 8, 6, 3, 0, 0, 5],
             [0, 5, 0, 0, 9, 0, 6, 0, 0],
             [1, 3, 0, 0, 0, 0, 2, 5, 0],
             [0, 0, 0, 0, 0, 0, 0, 7, 4],
             [0, 0, 5, 2, 0, 6, 3, 0, 0]]

    for i in range(9):
        t1 = []
        for j in range(9):
            txt = StringVar()
            if board[i][j]==0:
                txt.set('')
            else:
                txt.set(str(board[i][j]))
            Label(root,height = 2, width = 4, textvariable = txt, relief = "solid").grid(row = i, column = j)
            t1.append(txt)
        textvars.append(t1)

    solve_board(board, textvars)

These text variables and boards were passed to a solve_board() function which used backtracking and when updating the board, it updated the text alongside using the.set() function, like so:

def solve_board(board,textvars):

        for rowno in range(9):

            for colno in range(9):

                if board[rowno][colno] == 0:
                    for i in range(1,10):

                        if (is_valid(board,rowno,colno,i)):
                            board[rowno][colno]=i
                            textvars[rowno][colno].set(str(i))
                            solve_board(board,textvars)
                            board[rowno][colno]=0
                            textvars[rowno][colno].set('')
                    return False

        print (np.matrix(board))

All the bits that are not gui or tkinter related work perfectly, although they were typed in a hurry leading to less than optimal code.

When this code is run, the board displayed on the tkinter window is the unsolved board while the board being printed is fully solved.

I hope you could help me figure out as to why this code is not working and I have attached the rest of the code, an is_valid function and a main one below for further reference. Thank you.

def is_valid(b,r,c,n): #check if number insertion is valid
    if n in b[r]: #if in row
        return False
    for x in range(0,9):
        if n == b[x][c]: #check for column
            return False
    sr = r - r%3
    sc = c - c%3
    for x in range(sr,sr+3):
        for y in range(sc,sc+3):
            if b[x][y]==n:
                return False
    return True

if __name__ == "__main__":
    root = Tk()
    root.title("Sudoku")

    main()
    root.mainloop()

EDIT:

The code:

board[rowno][colno]=0
textvars[rowno][colno].set('')

This is used to reflect the backtracking process, ie if a choice made is incorrect, the program goes back to the last time it made a choice and it resets the choice by setting it to 0. Setting the text to '' is simply to reflect the reset made my the program in the tkinter window.

Answer 1

I think you need to return True at the end of solve_board() function. Also return at once if solve_board() return True in the if block.

Since mainloop() is not executed when solve_board() is running, therefore if you want to see the update during solving, you need to call root.update() after setting the StringVar:

def solve_board(board, textvars):
    for rowno in range(9):
        for colno in range(9):
            if board[rowno][colno] == 0:
                for i in range(1, 10):
                    if is_valid(board, rowno, colno, i):
                        board[rowno][colno] = i
                        textvars[rowno][colno].set(str(i))
                        root.update()
                        if solve_board(board, textvars):
                            return True
                        board[rowno][colno] = 0
                        textvars[rowno][colno].set('')
                        root.update()
                return False
    print(np.matrix(board))
    return True