Steve Holden a écrit : > TheFlyingDutchman wrote: >>> Else, you could as well write your own testing function: >>> >>> def str_starts_with(astring, *prefixes): >>> startswith = astring.startswith >>> for prefix in prefixes: >>> if startswith(prefix): >>> return true >>> return false >>> >> >> What is the reason for >> startswith = astring.startswith >> startswith(prefix) >> >> instead of >> astring.startswith(prefix) >> > It's an optimization: the assigment creates a "bound method" (i.e. a > method associated with a specific string instance) and avoids having to > look up the startswith method of astring for each iteration of the inner > loop. > > Probably not really necessary, though, and they do say that premature > optimization is the root of all evil ...
I wouldn't call this one "premature" optimization, since it doesn't change the algorithm, doesn't introduce (much) complication, and is proven to really save on lookup time. Now I do agree that unless you have quite a lot of prefixes to test, it might not be that necessary in this particular case... -- http://mail.python.org/mailman/listinfo/python-list
