Have a look at this short thread on discuss: https://discuss.python.org/t/searching-array-of-data-objects/4251/1 After I answered that question, it dawned on me that I have probably written something like that loop, or variations of it, a thousand times: for obj in somelist: if comparison(obj, needle): do_something(obj) break and now it's a thousand and one times *wink* So here's a thought... suppose we gave list.index an optional keyword- only comparison function? The typical name for those is "pred", as in predicate. Then the above becomes: try: i = somelist.index(needle, pred=comparison) except ValueError: pass else: do_something(somelist[i]) If you know for sure the search item exists, then you can drop the try...except...else: do_something(somelist[somelist.index(needle, pred=comparison)]) If `pred` is missing or None, a standard equality search is performed. Together with the operator module, this would allow us to perform common searches at C speed: # find the first item less than needle somelist.index(needle, pred=operator.lt) We can search a sublist efficiently: # copies the sublist :-( for obj in somelist[25:95354]: ... # save memory by inefficiently walking the entire list :-( for i, obj in enumerate(somelist): if i < 25: continue if i >= 95354: break ... # avoids both wasting memory and wasting time :-) i = somelist.index(needle, 25, 95354, pred=comparison) What do you think? -- Steven