[Python] How do I take a string of numbers and convert into a 2D 9x9 list?

From a string of numbers, no separators, to 2D 9x9 list. I get stuck on getting the numbers from the string into a 2D 9x9 array/list. I'm working on a Sudoku solver just to learn Python better.

numbers = '084030001560014000001586704420001070005309802900200043100078005006105407000490000'


I tried:

list1 = []
for n in numbers:
for i in range(0,9):
for j in range(0,9):
list1[j].append(n)


This gives me a list index out of range error.

Same with this:

list1 = []
for i in range(0,9):
for j in range(0,9):
for n in numbers:
list1[j].append(n)


I tried using a list comprehension, but I don't quite understand that well enough, and if I cannot get the for loops to work, then I probably won't get the comprehension to work.

I have found examples of comprehensions, but like I said, I don't understand them enough for a 2D list.

It seems like this should be really simple, lol!

I see a lot of questions on strings of numbers that are already comma separated, but I have not seen one without commas, yet.

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