sudoku.py

class Sudoku:
    """Sudoku validator"""

    grid = [[0] * 9 for i in range(9)]

    def __init__(self):
        self.populate_grid()
        self.print_grid()
        self.validate_grid()

    def populate_grid(self):
        with open('input.txt', 'r') as file:
            x, y = 0, 0

            for line in file:
                for value in line:
                    if value != " " and value != "\n":
                        self.grid[x][y] = value
                        y += 1
                x += 1
                y = 0

    def print_grid(self):
        for row in self.grid:
            print(row)

    def validate_grid(self):
        tmp = set()
        x, y = 0, 0

        # rows
        while x < 9:
            while y < 9:
                tmp.add(self.grid[x][y])
                y += 1
            if len(tmp) != 9:
                print("Error at line {0}.".format(x+1))
            x += 1
            y = 0
            tmp.clear()
        x = 0

        # columns
        while y < 9:
            while x < 9:
                tmp.add(self.grid[x][y])
                x += 1
            if len(tmp) != 9:
                print("Error at column {0}.".format(y+1))
            y += 1
            x = 0
            tmp.clear()
        y = 0


if __name__ == "__main__":
    Sudoku()