This doesn’t do what you hoped.
q = [[None]*5]*4
It reuses list objects multiple times. As you can see when you made a change to one cell, which was in a reused list object.
A single list with a value of [None] is used five times.
A single list with a value of [[None]*5] is used four times.
q = [ [ None for i in range(5) ] for j in range(4) ]
Might be more what you’re looking for.
This explicitly avoids reusing a list object.
80% of the time, a dictionary is what you really wanted.
q = {}
q[0,0]= 5
Will also work. You don’t start with a pre-defined grid of None values. But it’s rare to need them in the first place.
In Python 2.7 and higher, you can do this.
q = { (i,j):0 for i in range(5) for j in range(4) }
That will build a grid indexed by 2-tuples.
{(0, 1): 0, (1, 2): 0, (3, 2): 0, (0, 0): 0, (3, 3): 0, (3, 0): 0, (3, 1): 0, (2, 1): 0, (0, 2): 0, (2, 0): 0, (1, 3): 0, (2, 3): 0, (4, 3): 0, (2, 2): 0, (1, 0): 0, (4, 2): 0, (0, 3): 0, (4, 1): 0, (1, 1): 0, (4, 0): 0}