En Fri, 08 Feb 2008 22:04:26 -0200, Matt Nordhoff <[EMAIL PROTECTED]> escribió:
> J Peyret wrote: >> - Same with using try/except KeyError instead of in cls.cache. >> Has_key might be better if you insist on look-before-you-leap, because >> 'in cls.cache' probably expends to uri in cls.cache.keys(), which can >> be rather bad for perfs if the cache is very big. i.e. dict lookups >> are faster than scanning long lists. > > Not true. 'in' is (marginally) faster than has_key. It's also been > preferred to has_key for a while now. I don't understand your assertion, given your own timings below. I'd say that `has_key` is about 50% slower than `in`, not "marginally" > $ python -m timeit -s "d = dict.fromkeys(xrange(5))" "4 in d" > 1000000 loops, best of 3: 0.233 usec per loop > $ python -m timeit -s "d = dict.fromkeys(xrange(5))" "d.has_key(4)" > 1000000 loops, best of 3: 0.321 usec per loop > $ python -m timeit -s "d = dict.fromkeys(xrange(500000))" "499999 in d" > 1000000 loops, best of 3: 0.253 usec per loop > $ python -m timeit -s "d = dict.fromkeys(xrange(500000))" > "d.has_key(499999)" > 1000000 loops, best of 3: 0.391 usec per loop > $ python -m timeit -s "d = dict.fromkeys(xrange(500000))" "1000000 in d" > 1000000 loops, best of 3: 0.208 usec per loop > $ python -m timeit -s "d = dict.fromkeys(xrange(500000))" > "d.has_key(1000000)" > 1000000 loops, best of 3: 0.324 usec per loop -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
