New submission from Dan Schult :
In the depths of dictobject.c one can see that dict_setdefault uses two
identical calls to PyObject_Hash and ma_lookup. The first to see if the
item is in the dict, the second (only if key is not present) to add the
item to the dict.
This second lookup (and
Changes by Dan Schult :
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keywords: +patch
Added file: http://bugs.python.org/file13665/dict_setdefault.patch
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Python tracker
<http://bugs.python.org/issue5
Dan Schult added the comment:
Benchmarks:
Upon trying cooked up examples, I do not notice any speedup
beyond 5-10%. Seems like function calling time swamps everything
for small examples with fast hashes. I don't have a handy dandy
example with long hash times or long lookup times. T
Dan Schult added the comment:
On Apr 11, 2009, at 8:15 AM, Martin v. Löwis
@psf.upfronthosting.co.za
@psf.upfronthosting.co.za> wrote:
> Martin v. Löwis added the comment:
>
>> By the way, defaultdict is NOT like setdefault--it is like get().
>> Missing entries do n
Dan Schult added the comment:
Thank you... I stand corrected
That's actually very helpful!
Of course using defdict makes the default assignment take two hashes,
two lookups, an attribute/function lookup (__missing__) and the extra
function call, plus doesn't allow argume
