Python Classes: Appending a list & Incorporating a Method

Question

I just started learning about Python classes today and I had a quick question. I'm pretty amazed how much more succinct it has made my code, but I'm trying to figure out if the following is possible for a chess problem I'm working on.

(1) Can I append a list somehow from within a class method? I'm trying to figure out if there's a way to accumulate the pieces in a list each time capture is called.

(2) How can I call a method from within the class to be used in another method? I would like to be able to check if a move is valid before even proceeding if the piece should try to capture another or move.

class Piece(Board):

def __init__(self, piece, r, c):
    self.piece = piece
    self.r = r
    self.c = c

This is the function I would like to incorporate into the functions below to avoid the redundancy (Question 2)

def valid_move(self,r,c,r_offset,c_offset):
    #r, c are integers for the coordinates on the board
    #r_offset,c_offset are the cells the piece might move to
    self.tgt_r, self.tgt_c = r+r_offset, c+c_offset

    if self.tgt_r <= 7 or self.tgt_c >= 0:
            return True
    return False

These functions are the same for now. I'm trying to see how I can use the capture function to accumulate a list of pieces once they're taken. (Question 1)

def capture(self,r,c, r_offset, c_offset): 

    piece = self.piece
    self.tgt_r, self.tgt_c = r+r_offset, c+c_offset 

    if self.tgt_r > 7 or self.tgt_c < 0:
            return None             
    else:
        nb = Board(curr).copy_board() #this board is just 8x8 np.array
        nb[self.tgt_r,self.tgt_c], nb[r,c] = piece,'-'  
    return nb

def move(self,r,c, r_offset, c_offset):

    piece = self.piece
    self.tgt_r, self.tgt_c = r+r_offset, c+c_offset 

    if self.tgt_r > 7 or self.tgt_c < 0:
        return None
    else:
        nb = Board(curr).copy_board()
        nb[self.tgt_r,self.tgt_c], nb[r,c] = piece,'-'  
    return nb

Thanks as always.

Answer 1

1. Can I append a list somehow from within a class method?

create a list -piecesList in your class for storing the pieces:

class Piece(Board):
    def __init__(self, piece, r, c):
        self.piece = piece
        self.r = r
        self.c = c
        self.piecesList = [] #or init using some argument if you want to use some list from outside of the class

and whenever your capture method is called, simply append the piece in the piecesList :

def capture(self,r,c, r_offset, c_offset): 
    self.piecesList.append(self.piece)
    piece = self.piece

2. How can I call a method from within the class to be used in another method?

you can simply call it using self.method(arg1, arg2...) :

def capture(self,r,c, r_offset, c_offset): 

    piece = self.piece

    if self.valid_move(r,c,r_offset,c_offset) == False:
            return None             
    else:
        nb = Board(curr).copy_board() #this board is just 8x8 np.array
        nb[self.tgt_r,self.tgt_c], nb[r,c] = piece,'-'  
    return nb