List of Lists of Object referencing same object in Python

Question

I'm fairly new to Python and so I'm not extremely familiar with the syntax and the way things work exactly. It's possible I'm misunderstanding, but from what I can tell from my code this line:

largeBoard = [[Board() for i in range(3)] for j in range(3)] 

is creating 9 references to the same Board object, rather than 9 different Board objects. How do I create 9 different Board objects instead?

When I run:

largeBoard = [[Board() for i in range(3)] for j in range(3)]        
x_or_o = 'x'      
largeBoard[1][0].board[0][0] = 'g' # each Board has a board inside that is a list 
for i in range(3):
    for j in range(3):
        for k in range(3):
            for l in range(3):
                print largeBoard[i][j].board[k][l]

I get multiple 'g' that is what made me think that they are all references to the same object.

Answer 1

You have it reversed: you are creating 9 independent Board instances there. If you had something like

largeBoard = [[Board()] * 3] * 3

then you would only have a single instance. This is the root of a common mistake that many Python newcomers make.

[X for i in range(3)] evaluates X once for each i (3 times here) whereas [X] * 3 evaluates X only once.