Python list writing through loop, all previous values being overwritten [duplicate]

Answer 1

You are putting the same exact array in the list ten times. Updating one of the arrays is updating all of them. Try:

stuff = [[None]*3 for i in xrange(10)]

Answer 2

The reason that this is happening is because of your first line:

stuff = [[None]*3]*10

What this is actually doing is creating only 1 array of [[None]*3] and then referencing it 10 times.

So your array is actually similar to:

[[[None]*3], reference 0, reference 0, reference 0, reference 0, reference 0, reference 0, reference 0, reference 0, reference 0]

Change your first line to:

stuff = [[None]*3 for i in xrange(10)]

Which will create a unique element at each position within the array.