Emin> It sounds like it's probably not worth the effort in general, but Emin> might be for extremely ultra-critical parts of code.
Even in extremely ultra-critical parts of code I doubt the loss of readability would be worth it. If there are situations where you can really gain by switching from a natural indexing scheme to lists, there are probably other places in your code where you will gain just as much benefit without the corresponding loss of readability. Indexing lists only appears to be about twice as fast as indexing dicts: % timeit.py -s "data = {'a' : 1, 'b' :2, 'c' : 3}" "for k in 'abc': x = data[k]" 100000 loops, best of 3: 4.61 usec per loop % timeit.py -s "data = [1, 2, 3]" "for k in [0, 1, 2]: x = data[k]" 100000 loops, best of 3: 2.97 usec per loop If you're worried about regaining a couple microseconds per index you probably shouldn't be using Python. Skip -- http://mail.python.org/mailman/listinfo/python-list