How to create a square matrix with infinite rows

Question

I need to create a matrix with an unknown number of cells and rows. It will be determinated on the last iteration of a loop and the matrix must be filled each loop in a triangular shape. I don't care on how can I fill the matrix, but on how can I create it.

Thanks!

Answer 1

If you're doing a loop to create rows, numpy will not be very efficient because it will need to reallocate and copy memory content at each iteration. You might as well create a list of list in regular Python and convert it to a numpy matrix only at the end once you know the size.