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Mon May 24 08:50:07 EDT 2004 · http://mail.python.org/pipermail/python-dev/2004-May/044943.html

I wrote:
> Performance is certainly a legitimate concern.

Armin replied:
> Ok, then the current situation looks like the best one.  I
> suggest we just
> drop a note in the documentation saying that if there are
> objects for which
> x.__eq__(x) isn't necessarily true, you shouldn't expect them
> to be handled in
> a fully consistent way.
  [...]
> There is an extra costly indirection until the execution
> reaches that point.

Armin:

Performance is a *legitimate* concern, but not an *overwhelming*
one. If we are in danger of having to walk over the entirety of a
(possibly large) recusive structure (eg: tuple of tuples) to do
a comparison, then that's dangerously slow, and it's worth mucking
with the definition of equality to avoid it. But a single indirection
is "costly" only to someone capable of reaching your level of
close-to-the-machine performance understanding. I say, go with your
original plan -- the current behavior is a mess.

-- Michael Chermside

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