避免在python列表中重复

Question

I'm trying to put together a bit of logic for a chess game and have gotten stuck with making sure I don't place multiple pieces on the same square. My code at the moment is as follows but I'm not sure where it's not working.

def add(self, pawn, x_coordinate, y_coordinate, piece_color):
        for each_pawn in self.pawns:
            if each_pawn.x_coordinate == x_coordinate and each_pawn.y_coordinate == y_coordinate:
                pawn.x_coordinate = -1
                pawn.y_coordinate = -1
            else:
                pawn.x_coordinate = x_coordinate
                pawn.y_coordinate = y_coordinate

        self.pawns.append(pawn)

Pawns is set as an empty list at the top of the class. The idea is that the pawn I'm creating goes into the list then when any subsequent ones are created it is checking for them having the same coordinates, if it does it is placed in the -1, -1 square ie off the board. I'm sure it's not particularly elegant but I'm new with Python and hope to come back and refactor when I have some fundamentals working. Thanks for any help!

Answer 1

At the end of the loop pawn 's coordinates will correspond to result from the last pawn it was tested against. Add a break statement after pawn.y_coordinate = -1 .

Answer 2

class Pawn:
    def __init(x, y):
        self.x_coordinate = x
        self.y_coordinate = y

    @property
    def x_coordinate(self):
        return self.x_coordinate

    @x_coordinate.setter
    def x_corrdinate(x):
        self.x_coordinate = x    

    @property
    def y_coordinate(self):
        return self.y_coordinate

    @y_coordinate.setter
    def y_corrdinate(y):
        self.y_coordinate = y

    def __hash__(self):
        return hash(self.x_coordinate) ^ hash(self.y_coordinate)

    def __eq__(self, other):
        return self.x_coordinate == other. x_coordinate and self.x_coordinate == other.y_coordinate

Basically, write a class Pawn which has x and y coordinates, override __eq__() method and __hash__() , they would be used when check if pawn not in pawns: the __eq__() is used to validate 2 Pawn instance are equal or not based on their x and y coordinates.

How to use?

pawn = Pawn(-1, -1)
if pawn not in pawns:
    pawns.append(pawn)