sudoku-checker.py

# Python - How to check for a valid sudoku.

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

check = lambda sudoku: all([set(range(1,10))-set([sudoku[y+i][x+j] for i in (-1,0,1) for j in (-1,0,1)])==set() for y in range(1,9,3) for x in range(1,9,3)]+[set(range(1,10))-set(i)==set() for i in sudoku+list(zip(*sudoku))])

print(check(sudoku))