Question

I’ve never worked with 2D or 3D arrays before but i’m trying to make a maze.
In my snippet, squares is a list with each instance of a cell (so in a 3×4 maze, there would be 12 instances in squares)
I am then trying to append to row, a list of all the squares in a row, so row[0] would contain the first four square instances, row[1] would be the next four, etc.
the row[x].append(squares[y+z]) throws the IndexError, i’m guessing it’s the row[x] part, but i’m not sure what to do to fix it. I tried using extend instead of append.

numberOfRows = 3
numberOfColumns = 4
z = 0

for x in range(numberOfRows):
    for y in range(numberOfColumns):
        row[x].append(squares[y+z])
    z += 4

Answer 1

If I’m guessing it right, you want:

numberOfRows = 3
numberOfColumns = 4
z = 0

squares = range(numberOfRows * numberOfColumns)

row = [[] for _ in xrange(numberOfRows)]
for x in range(numberOfRows):
    for y in range(numberOfColumns):
        row[x].append(squares[y+z])
    z += 4

print row

i.e., you were only missing the row definition.

EDIT:

After reading OP’s comments, it seems that considering the following alternative is worth for the situation:

row = []
for x in range(numberOfRows):
    row.append([squares[y+z] for y in range(numberOfColumns)])
    z += numberOfColumns

So you don’t create all the lists in row beforehand.