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?

next((x for x in test_list if x.value == value), None)

This gets the first item from the list that matches the condition, and returns None if no item matches. It's my preferred single-expression form.

However,

for x in test_list:
    if x.value == value:
        print("i found it!")
        break

The naive loop-break version, is perfectly Pythonic -- it's concise, clear, and efficient. To make it match the behavior of the one-liner:

for x in test_list:
    if x.value == value:
        print("i found it!")
        break
else:
    x = None

This will assign None to x if you don't break out of the loop.

In Python, to access object attribute the syntax is

<object instance>.<attribute_name>

In your case, [index].

As Paul said, use dir(<object_instance>[index]) to get all attribute, methods associated object instance.

You can also use for loop to iterate over

for <obj> in <object_list>:
    <obj>.<attribute_name>

Hope it helps

You can get a list of all matching elements with a list comprehension:

[x for x in myList if x.n == 30]  # list of all elements with .n==30

If you simply want to determine if the list contains any element that matches and do it (relatively) efficiently, you can do

def contains(list, filter):
    for x in list:
        if filter(x):
            return True
    return False

if contains(myList, lambda x: x.n == 3)  # True if any element has .n==3
    # do stuff