bisection

In Python, how do you find the index of the first value greater than a threshold in a sorted list? I can think of several ways of doing this (linear search, hand-written dichotomy,..), but I'm looking for a clean an reasonably efficient way of doing it. Since it's probably a pretty common problem, I'm sure experienced SOers can help! Thanks! Have a look at bisect . import bisect l = [1, 4, 9, 16, 25, 36, 49, 64, 81, 100] bisect.bisect(l, 55) # returns 7 Compare it with linear search: timeit bisect.bisect(l, 55) # 375ns timeit next((i for i,n in enumerate(l) if n > 55), len(l)) # 2.24us timeit