Hi, Couple ideas: 1. Itself is one word. 2. Double-quotation marks? 3. How about tuples? Something like, a = "a", "b", "c", "d", "e", The above becomes an immutable tuple by the compiler. In general, tuples should perform a little better than lists, at least in terms of memory usage. 4. This is confusing. Why use x twice? Matrix = [[0 for x in range(5)] for x in range(5)] Use an underscore if the index isn't needed. Matrix = [[0 for _ in range(5)] for _ in range(5)] 5. It's okay to put comments above the expression being referred to. No need for inline comments in most places. No - print(Matrix[0][0]) # prints 1 Yes - # out: 1 print(Matrix[0][0]) 6. Good to check if exists first. Current - def column(matrix, i): return [row[i] for row in matrix] Suggested - def column(matrix, i): if len(matrix) == 0 or len(matrix[0]) >= i: return return [row[i] for row in matrix] Etc. Really, just a terrible file that could use a lot more improvement. Sorry if that comes across as rough as it's not a personal attack. Best, Mark M.