https://qiita.com/hatt_takumi/items/37a9c15b4e0ad2119ac6#comment-ff8ff1d71175ab6b90c8

suudoku_numpy.py

import numpy as np

_ = 0
problem = [
    [_, _, _,   _, 4, _,   _, _, _],
    [_, _, 5,   _, _, _,   _, _, _],
    [_, 3, 6,   8, _, _,   _, 7, 2],

    [_, 8, _,   _, _, 6,   5, _, _],
    [1, _, _,   5, _, _,   _, 9, _],
    [_, _, _,   _, _, _,   2, _, 7],

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

answer = np.zeros((9, 9))
candidates = np.ones((9, 9, 9))

def fixed(y, x, number):
    answer[y, x] = number
    candidates[y, x] = 0
    candidates[y, :, number-1] = 0
    candidates[:, x, number-1] = 0
    candidates[y//3*3:y//3*3+3, x//3*3:x//3*3+3, number-1] = 0

for y, row in enumerate(problem):
    for x, number in enumerate(row):
        if number != 0:
            fixed(y, x, number)

while np.any(answer == 0):
    for y, row in enumerate(candidates):
        for x, candidate in enumerate(row):
            if answer[y, x] != 0:
                continue
            if candidate.sum() == 1:
                fixed(y, x, np.where(candidate == 1)[0] + 1)
                continue
            for i in range(9):
                if candidate[i] == 0:
                    continue
                if (candidates[y, :, i].sum() == 1
                or  candidates[:, x, i].sum() == 1
                or  candidates[y//3*3:y//3*3+3, x//3*3:x//3*3+3, i].sum() == 1):
                    fixed(y, x, i + 1)

print("-------------------")
print(*answer, sep="\n")
print("-------------------")