Fill data conditionally using previous values in a list comprehension

Question

I am using the following code to generate a two dimensional list.

grid = [[ 1 if i == 0 or j == 0 else 0  for i in range(size) ] for j in range(size)]

which generates

[1, 1, 1]
[1, 0, 0] 
[1, 0, 0]

Is it possible to use the values to get the next values inside list comp like

grid[1][1] = grid[0][1] + grid[1][0]

so it will look like

[1, 1, 1]
[1, 2, 3] 
[1, 3, 6]

I know I can iterate it and get the result but is it possible with list comprehension?

Answer 1

Seems like this would be more easily done in an iterative way:

size = 5

grid = [[1 for i in range(size)] for j in range(size)]
for i in range(1, size):
    for j in range(1, size):
        grid[i][j] = grid[i-1][j] + grid[i][j-1]

print grid

Result (spacing added by me manually):

[
    [1, 1,  1,  1,  1], 
    [1, 2,  3,  4,  5], 
    [1, 3,  6, 10, 15], 
    [1, 4, 10, 20, 35], 
    [1, 5, 15, 35, 70]
]