Python question concerning computational complexity

Question

Determine the tightest simple bound of the worst-case computational complexity of the following function in terms of the size of the input list (n=len(lst)) and justify your answer. For that, describe what situation constitutes the worst case and what line(s) is/are dominating the overall computational cost. Provide additional arguments as necessary (you should not need more than 3-4 sentences).

def large_prefix(lst, t):

    n = len(lst)

    s = 0

    for i in range(len(lst)):

        s = s + lst[i]

        if s > t:

            return lst[:i+1]

    return None

Answer 1

Is this a trick question?

The function is finding the first value that, when combined with it's index, is greater than t. The most computationally simple way to do that is to check each value in turn, and stop when you find one that satisfies the condition. This function does just that and is O(1).

However, I would probably clean up the code a bit like this:

def large_prefix(lst, t):

    for i in range(len(lst)):

        if i + lst[i] > t:

            return lst[:i+1]

(n and s are not needed, and Python functions automatically return None when not specified.)