They should be able to use a slotted cmp_to_key style class: http://docs.python.org/howto/sorting.html
That will allocate 1 Python object with no dict per key, but that might not be good enough. Reid On Sat, Mar 12, 2011 at 3:44 PM, Guido van Rossum <gu...@python.org> wrote: > I was just reminded that in Python 3, list.sort() and sorted() no > longer support the cmp (comparator) function argument. The reason is > that the key function argument is always better. But now I have a > nagging doubt about this: > > I recently advised a Googler who was sorting a large dataset and > running out of memory. My analysis of the situation was that he was > sorting a huge list of short lines of the form "shortstring,integer" > with a key function that returned a tuple of the form ("shortstring", > integer). Using the key function argument, in addition to N short > string objects, this creates N tuples of length 2, N more slightly > shorter string objects, and N integer objects. (Not to count a > parallel array of N more pointers.) Given the object overhead, this > dramatically increased the memory usage. It so happens that in this > particular Googler's situation, memory is constrained but CPU time is > not, and it would be better to parse the strings over and over again > in a comparator function. > > But in Python 3 this solution is no longer available. How bad is that? > I'm not sure. But I'd like to at least get the issue out in the open. > > -- > --Guido van Rossum (python.org/~guido) > _______________________________________________ > Python-Dev mailing list > Python-Dev@python.org > http://mail.python.org/mailman/listinfo/python-dev > Unsubscribe: > http://mail.python.org/mailman/options/python-dev/reid.kleckner%40gmail.com > _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com