Most efficient way to check if timestamp in list exists between two other timestamps?

I am trying to search a list of datetimes to check if there is a timestamp C that exists between timestamp A and B. I found the bisect stdlib but am not sure how to apply it here with datetime types.

My setup is similar to this:

insulin_timestamps = ['2017/07/01 13:23:42', '2017/11/01 00:56:40', '2018/02/18 22:01:09']

start_time = '2017/10/31 22:00:11'
end_time = '2017/11/01 01:59:40'

I want to check if a timestamp in the list exists between my two variable times. I am doing this multiple times in a loop. The only solution I can come up with is another loop within it that checks the whole list. I would rather not do that for efficiency purposes as it is a lot of data. Any tips?

Answer

If you just want to check if a timestamp exists between start_time and end_time, and the list is sorted, then you just need to check the timestamp immediately following start_time (assuming it occurs in the list). If that is less than end_time, then the result is true. It would add a few checks to the code but would cut runtime in half by removing the need for bisect_right. The code would appear as follows:

left_index = bisect_left(insulin_timestamps, start_time)
present = (
    len(insulin_timestamps) != 0 # if the list is empty the result is False
    and left_index != len(insulin_timestamps)
    and insulin_timestamps[left_index] < end_time
)

Here left_index != len(insulin_timestamps) checks that start_time is not than any element in the list: if it is, then the result is False.