为什么我的python程序中的while循环没有结束？

Question

I am a novice programmer and am learning python as a first language. For practice I made a program that generates a completed sudoku puzzle, hopefully to be used later as part of a sudoku game with a GUI. But as of right now it does nothing. And by that I mean when it is run nothing is printed out on the screen. I've checked to make sure everything is formatted correctly, and to the best of my understanding all of my syntax is correct. Is there some logical error that has escaped my notice? In any case, I suspect that something is preventing my while loop from breaking. Also, I realize that my program is probably unnecessarily long, but since I am still only beginning to learn the program I had a very limited toolkit to work with.

Here is my program in its entirety:

    # Sudoku puzzle maker
    # Practice game that makes an unfinished sudoku puzzle for the player    to solve

    import random

    # The readout string stores the assigned numbers given to each square
    # in the puzzle.

    readout = ""

    # The "c" strings store the numbers contained in each of the columns.
    # The program will check these strings to make sure that only one of each
    # number from 1 to 9 is in each column.
    # The same is true for the "r" (row) and "b" (box) strings.

    c1 = ""
    c2 = ""
    c3 = ""
    c4 = ""
    c5 = ""
    c6 = ""
    c7 = ""
    c8 = ""
    c9 = ""

    r1 = ""
    r2 = ""
    r3 = ""
    r4 = ""
    r5 = ""
    r6 = ""
    r7 = ""
    r8 = ""
    r9 = ""

    b1 = ""
    b2 = ""
    b3 = ""
    b4 = ""
    b5 = ""
    b6 = ""
    b7 = ""
    b8 = ""
    b9 = ""

    # The "square" strings store the location of each square as a 3-digit code,
    # the first digit is the column, the second the row, and the third the box.
    # For example, the fourth square is in c4 (column 4), r1 (row 1),
    # and b2 (3x3 box 2), so its corresponding string is "412".

    square_1 = "111"
    square_2 = "211"
    square_3 = "311"
    square_4 = "412"
    square_5 = "512"
    square_6 = "612"
    square_7 = "713"
    square_8 = "813"
    square_9 = "913"
    square_10 = "121"
    square_11 = "221"
    square_12 = "321"
    square_13 = "422"
    square_14 = "522"
    square_15 = "622"
    square_16 = "723"
    square_17 = "823"
    square_18 = "923"
    square_19 = "131"
    square_20 = "231"
    square_21 = "331"
    square_22 = "432"
    square_23 = "532"
    square_24 = "632"
    square_25 = "733"
    square_26 = "833"
    square_27 = "933"
    square_28 = "144"
    square_29 = "244"
    square_30 = "344"
    square_31 = "445"
    square_32 = "545"
    square_33 = "645"
    square_34 = "746"
    square_35 = "846"
    square_36 = "946"
    square_37 = "154"
    square_38 = "254"
    square_39 = "354"
    square_40 = "455"
    square_41 = "555"
    square_42 = "655"
    square_43 = "756"
    square_44 = "856"
    square_45 = "956"
    square_46 = "164"
    square_47 = "264"
    square_48 = "364"
    square_49 = "465"
    square_50 = "565"
    square_51 = "665"
    square_52 = "766"
    square_53 = "866"
    square_54 = "966"
    square_55 = "177"
    square_56 = "277"
    square_57 = "377"
    square_58 = "478"
    square_59 = "578"
    square_60 = "678"
    square_61 = "779"
    square_62 = "879"
    square_63 = "979"
    square_64 = "187"
    square_65 = "287"
    square_66 = "387"
    square_67 = "488"
    square_68 = "588"
    square_69 = "688"
    square_70 = "789"
    square_71 = "889"
    square_72 = "989"
    square_73 = "197"
    square_74 = "297"
    square_75 = "397"
    square_76 = "498"
    square_77 = "598"
    square_78 = "698"
    square_79 = "799"
    square_80 = "899"
    square_81 = "999"

    # The "master_list" is a tuple that stores all of the "square" strings in order
    # of their appearance. I realize now that I could have just had it store the
    # strings directly, but I'm too lazy to go back and change it.

    master_list = (square_1, square_2, square_3, square_4, square_5, square_6, square_7, square_8, square_9,\

     square_10, square_11, square_12, square_13, square_14, square_15, square_16, square_17, square_18,\

     square_19, square_20, square_21, square_22, square_23, square_24, square_25, square_26, square_27,\

     square_28, square_29, square_30, square_31, square_32, square_33, square_34, square_35, square_36,\

     square_37, square_38, square_39, square_40, square_41, square_42, square_43, square_44, square_45,\

     square_46, square_47, square_48, square_49, square_50, square_51, square_52, square_53, square_54,\

     square_55, square_56, square_57, square_58, square_59, square_60, square_61, square_62, square_63,\

     square_64, square_65, square_66, square_67, square_68, square_69, square_70, square_71, square_72,\

     square_73, square_74, square_75, square_76, square_77, square_78, square_79, square_80, square_81)

    # This for loop, for each square, picks a random number, converts it from an
    # integer into a string, and checks to see if it is already in the same column,
    # row, or box. It checks this by deciding which "c" "r" and "b" string
    # to look into based on the 3-digit code in each "square" string, and if
    # it finds that the number it picked is already in the same c, r, or b, it
    # tries again with a new random number. If the number fits, it is added to
    # the proper "c", "r", and "b" strings for future reference, and added to the
    # "readout" string.

    for square in master_list:
        while True:
            number = str(random.randint)

    # Here the program finds which column the square is in, and checks that column.      

            if square[0] == "1":
                column = c1
                if number in c1:
                    continue
            elif square[0] == "2":
                column = c2
                if number in c2:
                    continue
            elif square[0] == "3":
                column = c3
                if number in c3:
                    continue
            elif square[0] == "4":
                column = c4
                if number in c4:
                    continue
            elif square[0] == "5":
                column = c5
                if number in c5:
                    continue
            elif square[0] == "6":
                column = c6
                if number in c6:
                    continue
            elif square[0] == "7":
                column = c7
                if number in c7:
                    continue
            elif square[0] == "8":
                column = c8
                if number in c8:
                    continue
            elif square[0] == "9":
                column = c9
                if number in c9:
                    continue

    #Here the program finds which row it is in and checks the row.


            if square[1] == "1":
                row = r1
                if number in r1:
                    continue
            elif square[1] == "2":
                row = r2
                if number in r2:
                    continue
            elif square[1] == "3":
                row = r3
                if number in r3:
                    continue
            elif square[1] == "4":
                row = r4
                if number in r4:
                    continue
            elif square[1] == "5":
                row = r5
                if number in r5:
                    continue
            elif square[1] == "6":
                row = r6
                if number in r6:
                    continue
            elif square[1] == "7":
                row = r7
                if number in r7:
                    continue
            elif square[1] == "8":
                row = r8
                if number in r8:
                    continue
            elif square[1] == "9":
                row = r9
                if number in r9:
                    continue

    #Here it finds which box it is in and checks the box.


            if square[2] == "1":
                box = b1
                if number in b1:
                    continue
            elif square[2] == "2":
                box = b2
                if number in b2:
                    continue
            elif square[2] == "3":
                box = b3
                if number in b3:
                    continue
            elif square[2] == "4":
                box = b4
                if number in b4:
                    continue
            elif square[2] == "5":
                box = b5
                if number in b5:
                    continue
            elif square[2] == "6":
                box = b6
                if number in b6:
                    continue
            elif square[2] == "7":
                box = b7
                if number in b7:
                    continue
            elif square[2] == "8":
                box = b8
                if number in b8:
                    continue
            elif square[2] == "9":
                box = b9
                if number in b9:
                    continue


    # If a random number has gotten this far, it means it has passed inspection.
    # Now the program concatenates the number to the correct "c", "r" and "b"
    # strings for future reference.


            if column == c1:
                    c1 += number
            elif column == c2:
                    c2 += number
            elif column == c3:
                    c3 += number
            elif column == c4:
                    c4 += number
            elif column == c5:
                    c5 += number
            elif column == c6:
                    c6 += number
            elif column == c7:
                    c7 += number
            elif column == c8:
                    c8 += number
            elif column == c9:
                    c9 += number

            if row == r1:
                    r1 += number
            elif row == r2:
                    r2 += number
            elif row == r3:
                    r3 += number
            elif row == r4:
                    r4 += number
            elif row == r5:
                    r5 += number
            elif row == r6:
                    r6 += number
            elif row == r7:
                    r7 += number
            elif row == r8:
                    r8 += number
            elif row == r9:
                    r9 += number

            if box == b1:
                    b1 += number
            elif box == b2:
                    b2 += number
            elif box == b3:
                    b3 += number
            elif box == b4:
                    b4 += number
            elif box == b5:
                    b5 += number
            elif box == b6:
                    b6 += number
            elif box == b7:
                    b7 += number
            elif box == b8:
                    b8 += number
            elif box == b9:
                    b9 += number

    # Now the number is added to the readout and the while loop breaks, moving
    # the for loop on to the next square.

            readout += number
            break

    print(readout)



    input("\n\nyay it worked.")

Answer 1

Your code runs forever because there's nothing in your algorithm that can make it backtrack if you get into an unsolvable board state. For an example, consider the values on the first two rows of this board:

1 2 3 4 5 6 7 8 9
5 6 7 8 9 1 2 3

The numbers that have been entered so far are all legal, since they don't overlap in row, column or box. But there's no legal value that can be put in the last column of the second row. If your code randomly placed the first 17 numbers in this pattern, it would be stuck forever trying to place the 18th. Most likely your program gets a bit further than this before getting stuck, but it may be more likely to get stuck than to generate a full board (I'm not sure how the probabilities work out).