On Tue, Mar 18, 2014 at 01:21:05PM +0200, Maciej Fijalkowski wrote:
> note that this is specifically about dicts, where __eq__ will be
> called undecided number of times anyway (depending on collisions in
> hash/buckets which is implementation specific to start with)
Exactly. Using a __eq__ method with side-effects is a good way to find
out how many collisions your dict has :-)
But specifically with your example,
if x in d:
return d[x]
my sense of this is that it falls into the same conceptual area as the
identity optimization for checking list or set containment: slightly
unclean, but justified. Provided d is an actual built-in dict, and it
hasn't been modified between one call and the next, I think it would be
okay to optimize the second lookup d[x].
A question: how far away will this optimization apply?
if x in d:
do_this()
do_that()
do_something_else()
spam = d[x]
Assuming no modifications to d, will the second lookup still be
optimized?
--
Steven
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