How do I use duplicates of a class instance in my function arguments?

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Python

Python2.7

chess

, +

My class spot takes in an x and y value to create coordinates on my board.
I have a function responsible for moving my chess piece from its current set of coordinates to a new set of coordinates by subtracting the starting x and ending x and the same for the starting y and ending y. The problem I am facing is I get an error when I take in duplicates of a class instance in the function arguments responsible for moving my chess piece from its current set of coordinates to a new set of coordinates.

class Spot:

    def __init__(self, x, y, piece):
        self.x = x
        self.y = y
        self.piece = piece

def canMove(self, board, spot start, spot end):
       pass

What I have tried:

I have tried passing in the names of the class instances instead of having it as a type followed by a name. If I do that, how would I distinguish the starting and ending coordinates? I also get a duplicate error for this