How to determine the time complexity of searching for an element in a list-based collection?

The time complexity of searching for an element in a list (for example, in a Python list) is usually O(n), where n is the number of elements in the list. This is because, to find an element, you need to sequentially iterate through the list until the desired element is found or the end is reached.

Example: searching for the value x in the list lst is implemented via iteration:

lst = [1, 3, 5, 7, 9]
x = 7
found = False
for item in lst:
    if item == x:
        found = True
        break

If the list is not sorted, there are no more efficient search methods without additional data structures. If the list is sorted, binary search can be used with a time complexity of O(log n).