How do I efficiently extract all elements in a column from a dictionary whose values are 2D lists in Python?

Question

I have a dictionary whose values are lists of lists.

mydict = {
"A" : [["gactacgat", "IE"],["gactacgat", "IE"]],
"G" : [["ggctacgat", "EI"],["gactacgat", "IE"]],
"C" : [["gcctacgat", "N"],["gactacgat", "IE"]],
"T" : [["gtctacgat", "IE"],["gactacgat", "IE"]]
}

And I am trying to create a list containing all of the elements in the second column of these 2D lists. This is what I am doing:

  mylist = []
  for key in mydict.keys():
      for row in mydict[key]:
          mylist.append(row[1])

Is there a more efficient way of accessing a specific index from all the lists in these lists of lists than what I have done?

(I apologize if my wording was bad, and any feedback for a better title question is appreciated)

Answer 1

List comprehensions are your friend:

mylist = [row[1] for value in mydict.values() for row in value]

This uses a nested loop, but presumably a bit better optimized. Additionally, using dict.values saves you a key lookup at each iteration of the outer loop, and returns items in the same order as the keys would be.