And i want to create a numpy array of zeros of that list's length. More on stackoverflow.com

This is wrong because each row references the same array. If you change one value in the array, it will be changed for all rows. You should put the new double[3] statement directly inside the loop. Alternatively, if you're dealing with matrices, you should use n-dimensional arrays instead: - var bigDaddy = new double[1001, 3] this will create a 1001x3 matrix filled with zeroes by default - var bigDaddy = new double[3003] this will create a 3003 sized array filled with zeroes which you can then navigate with the % operator and use Span for operations for a performance boost More on reddit.com

while not lyst[-1]: lyst.pop() More on reddit.com

It's a list comprehension that creates n distinct [0] * n lists, and it's a pretty common idiom. You can think of [[0] * n] * n as a = [0] * n b = [] for _ in range(n): b.append(a) # same `a` every time And the later as b = [] for _ in range (n): a = [0] * n b.append(a) # new `a` every time The i is irrelevant, and you'd commonly just use a name like _ communicating "this variable doesn't matter". More on reddit.com