A list comprehension would work just fine:

[o.my_attr for o in my_list]

But there is a combination of built-in functions, since you ask :-)

from operator import attrgetter
map(attrgetter('my_attr'), my_list)

attrs = [o.attr for o in objs] was the right code for making a list like the one you describe. Don't try to subclass list for this. Is there something you did not like about that snippet?

A list comprehension will cover this quite nicely.

data = [
 ["Test_1", 
  {"name": "Test_level_1", "value": 10}, 
  {"name": "Test_level_1 again", "value": 15}], 
 ["Test_2", 
  {"name": "Test_level_2", "value": 1}, 
  {"name": "Test_level_2 again", "value": 5}]
]

desired_data = [
  item['name'] 
  for sublist in data 
  for item in sublist 
  if isinstance(item, dict)
]

Result:

['Test_level_1', 'Test_level_1 again', 'Test_level_2', 'Test_level_2 again']

>>> A = [{'X1': val1, 'X2': 'val2', 'X3': 'val3', 'X4': val4}]
>>> list(A[0].values())
[val1,'val2','val3',val4]

Try using a list of lists, like this:

lsts = [[" "],
        [".", ",", "?"],
        ["a", "b", "c"],
        ["d", "e", "f"],
        ["g", "h", "i"],
        ["j", "k", "l"],
        ["m", "n", "o"],
        ["p", "q", "r", "s"],
        ["t", "u", "v"],
        ["w", "x", "y", "z"]]

Now you can access each sublist by its index:

lsts[1]
=> [".", ",", "?"]

And each element by both of its indexes:

lsts[1][2]
=> "?"

Now it's easy to extract values from a list of key presses, like those shown in the question and then join them:

keypresses = [[6, 3], [0, 1], [5, 2]]
''.join(lsts[i][j-1] for i, j in keypresses)
=> "n k"

Notice that the indexes start from zero, so I had to subtract one unit from the sample key presses given in the question.