Find indices of a value in 2d matrix

Question

I have a matrix of the form,

mymatrix=[[1,2,3],[4,5,6],[7,8,9]]

I want to the get the index of, say for example, 9 which is at (2,2).

Answer 1

You could do this instead of using enumerate. NOT sure at all if this is any faster.

matrix = [[1,2,3],[4,5,6],[7,8,9],[10,11,12]]
needle = 9

matrix_dim = len(matrix[0])
item_index = 0
for row in matrix:
    for i in row:
        if i == needle:
            break
        item_index += 1
    if i == needle:
        break

print(int(item_index / matrix_dim), item_index % matrix_dim)

This will take exactly time i * dim(matrix) + (j+1) where the result of the above is i j which could be O(n^2) in the worst case.