Multi dimensional arrays in Python of a dynamic size

In python there is no need to declare list size on forehand.

an example of reading lines to a file could be this:

file_name = "/path/to/file"
list = []

with open(file_name) as file:
  file.readline
  if criteria:
    list.append(line)

For multidimensional lists. create the inner lists in a function on and return it to the append line. like so:

def returns_list(line):
  multi_dim_list = []
  #do stuff
  return multi_dim_list

exchange the last row in the first code with

list.append(returns_list(line))

Nest lists in lists you don't need to predefine the length of a list to use it and you can append on to it. Want another dimension simply append another list to the inner most list.

[[[a1, a2, a3]  , [b1, b2, b3] , [c1, c2, c3]],
[[d1, d2, d3]  , [e1, e2, e3] , [f1, f2, f3]]]

and to use them easily just look at Nested List Comprehensions