2d array not working?

[Hot_Milo23]

Posted via CodeCall Mobile
im trying to use a 2d array in my program, and i cant seem to find where im going wrong.

box=[0]*3
box2=[box]*3
box[0][0]=1
box[0][0] 
>>>[[1,0,0],[1,0,0],[1,0,0]]

what i wanted was to assign the first rows first box with 0, not all of them.

any help?

[Vswe]

This is since all of your three arrays are actually the same one. Therefor when you change the first one all three are changed.

Edit: Sorry I forgot to tell how to solve it. Do something like this to actually copy it:

box=[0]*3
box=copy.deepcopy(box)*3
box[0][0]=1

I'm at school now so I can't test it but I think that will work.

[Hot_Milo23]

Posted via CodeCall Mobile
thanks. i.ll try it when i can get on. Ty!

[Hot_Milo23]

Posted via CodeCall Mobile
ok, tested it, same results. Have to import copy btw. Thx tho.

[Vswe]

Ok, I will test it when I comes home.

[Hot_Milo23]

Posted via CodeCall Mobile
on a side note: ive never used deepcopy before, and i actually needed it in anotha part of the program. So thanks for the tip.

[Hot_Milo23]

Posted via CodeCall Mobile
well ive done what i can for tonite, and i wont have time to get on tomoz. So thanks, and i.ll try again later.

[Vswe]

I solved the problem now. The problem before was that we made a copy and then added that three times instead of creating three copies. Here's the solution:

import copy

base=[0]*3
box=[]

for i in range(0,3):
    box+=copy.deepcopy([base])

box[0][0] = 1
print box

[Hot_Milo23]

Posted via CodeCall Mobile
ahhhhh. Thanks. Much appreciated.

[manux]

same thing using the whole power of Python:

>>> [[int(i==0) for i in range(3)] for j in range(3)]
[[1, 0, 0], [1, 0, 0], [1, 0, 0]]
#with x=4 and y=5
>>> [[int(i==0) for i in range(x)] for j in range(y)]
[[1, 0, 0, 0], [1, 0, 0, 0], [1, 0, 0, 0], [1, 0, 0, 0], [1, 0, 0, 0]]