Szachy/square.py

class Square:
    def __init__(self, row, column, piece=None):
        self.row = row
        self.column = column
        self.piece = piece

    def has_piece(self):
        if self.piece is None:
            return False
        else:
            return True

    def is_rival(self, color):
        if self.has_piece() is True and self.piece.color != color:
            return True

    def empty_or_rival(self, color):
        if self.has_piece() is False or self.is_rival(color):
            return True
        else:
            return False
    def empty_or_rival_knight(self, color):
        if self.has_piece() is False or self.is_rival(color):
            return True
        else:
            return False

    @staticmethod
    def on_board(*args):
        for arg in args:
            if arg < 0 or arg > 7:
                return False
        return True