如何使用嵌套的 for 循环在 Python 中从一个列表写入另一个列表？

Question

I have two lists:

import random

board = [
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
    [0, 0, 0, 0, 0, 0, 0, 0, 0],
]

boxes = [random.sample(range(1, 10), 9), random.sample(range(1, 10), 9), random.sample(range(1, 10), 9)]

The first one is a sudoku board and the second one is three lists of 9 random non-repeating numbers. And I want to insert the random numbers into the sudoku board so the result board looks something like this:

[5, 4, 3, 0, 0, 0, 0, 0, 0],
[2, 9, 1, 0, 0, 0, 0, 0, 0],
[6, 7, 8, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 1, 6, 3, 0, 0, 0],
[0, 0, 0, 4, 5, 8, 0, 0, 0],
[0, 0, 0, 9, 2, 7, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 3, 8, 2],
[0, 0, 0, 0, 0, 0, 5, 9, 6],
[0, 0, 0, 0, 0, 0, 7, 1, 4]

I can achieve what I want with this code:

# BOX 1
board[0][0] = boxes[0][0]
board[0][1] = boxes[0][1]
board[0][2] = boxes[0][2]

board[1][0] = boxes[0][3]
board[1][1] = boxes[0][4]
board[1][2] = boxes[0][5]

board[2][0] = boxes[0][6]
board[2][1] = boxes[0][7]
board[2][2] = boxes[0][8]

# BOX 2
board[3][3] = boxes[1][0]
board[3][4] = boxes[1][1]
board[3][5] = boxes[1][2]

board[4][3] = boxes[1][3]
board[4][4] = boxes[1][4]
board[4][5] = boxes[1][5]

board[5][3] = boxes[1][6]
board[5][4] = boxes[1][7]
board[5][5] = boxes[1][8]

# BOX 3
board[6][6] = boxes[2][0]
board[6][7] = boxes[2][1]
board[6][8] = boxes[2][2]

board[7][6] = boxes[2][3]
board[7][7] = boxes[2][4]
board[7][8] = boxes[2][5]

board[8][6] = boxes[2][6]
board[8][7] = boxes[2][7]
board[8][8] = boxes[2][8]

But obviously that is a super long and dumb way to do this but for the love of god I cannot figure out how to do this using a nested for loop, but it seems like it should be possible?

I thought I could atleast fill the first box with this code:

for x in range(9):
    for y in range(3):
        board[y][x] = boxes[0][x]

But even that does not work as intended...please help...

Answer 1

This will do it. There are better ways if you are willing to use numpy.

for box in range(3):
    # Get starting location in board.
    dx = box*3
    for k in range(9):
        x = k % 3
        y = k // 3
        board[dx+y][dx+x] = boxes[box][k]

Alternatively:

for box in range(3):
    # Get starting location in board.
    dx = box*3
    for y in range(3):
        for k in range(3):
          board[dx+y][dx+x] = boxes[box][y*3+x]

Answer 2

You can directly generate board like this:

import random
board = [random.sample(range(1, 10), 3)+[0]*6, random.sample(range(1, 10), 3)+[0]*6, random.sample(range(1, 10), 3)+[0]*6,
[0]*3+random.sample(range(1, 10), 3)+[0]*3, [0]*3+random.sample(range(1, 10), 3)+[0]*3, [0]*3+random.sample(range(1, 10), 3)+[0]*3, [0]*6+random.sample(range(1, 10), 3), [0]*6+random.sample(range(1, 10), 3), [0]*6+random.sample(range(1, 10), 3)]
print(board)

Output

[
[9, 6, 7, 0, 0, 0, 0, 0, 0],
[2, 6, 3, 0, 0, 0, 0, 0, 0],
[8, 7, 4, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 7, 3, 8, 0, 0, 0],
[0, 0, 0, 5, 1, 6, 0, 0, 0],
[0, 0, 0, 6, 8, 1, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 2, 9, 7],
[0, 0, 0, 0, 0, 0, 3, 4, 8],
[0, 0, 0, 0, 0, 0, 9, 5, 6]
]

A more neater version using functions:

import random
def f1():
    return random.sample(range(1, 10), 3)+[0]*6

def f2():
    return [0]*3+random.sample(range(1, 10), 3)+[0]*3

def f3():
    return [0]*6+random.sample(range(1, 10), 3)

board = [f1(),f1(),f1(),f2(),f2(),f2(),f3(),f3(),f3()]
print(board)

Answer 3

import numpy as np

def rand3x3():
    return np.random.randint(1,9,(3,3))

board = np.zeros((9,9), dtype=int)

for square3x3 in [[0,3],[3,6],[6,9]]:
    start = square3x3[0]
    end = square3x3[1]    
    board[start:end, start:end] += rand3x3()

board.tolist()

Output

[[2, 6, 4, 0, 0, 0, 0, 0, 0],
 [4, 3, 3, 0, 0, 0, 0, 0, 0],
 [8, 4, 6, 0, 0, 0, 0, 0, 0],
 [0, 0, 0, 4, 6, 1, 0, 0, 0],
 [0, 0, 0, 6, 7, 3, 0, 0, 0],
 [0, 0, 0, 7, 2, 6, 0, 0, 0],
 [0, 0, 0, 0, 0, 0, 1, 8, 2],
 [0, 0, 0, 0, 0, 0, 3, 2, 6],
 [0, 0, 0, 0, 0, 0, 7, 4, 1]]