Question

Is there a way for me to access only certain elements in a 2D array, for example the vertical elements only or the first elements in a set of ordered pairs, in Python?

Answer 1

2D arrays? you mean lists of lists, or python's array module, or do you mean numpy's arrays?

Answer 2

lists of lists:
A = [[1,0,0],
[0,1,0],
[0,0,1]]

if you only want to get out the 'columns' then you can transpose it using list comprehensions.

Answer 3

or you can simply loop:
col2 = []
for row in A:
col2.append(row[1]) # gets out the elements in the 2nd "column"

Answer 4

list comprehensions:
col2 = [row[1] for row in A]

Answer 5

sets of ordered pairs? you mean Python's native set() ?