Andre Meyer wrote:
> So, what it means is that the test is not meaningful, because of the
> different way that object attributes are accessed (not as o.x, which
> could be compiled).
correct, but you may be overestimating what the compiler can do. here's
the byte code for the various cases:
# x.attr
2 0 LOAD_FAST 0 (x)
3 LOAD_ATTR 0 (attr)
6 POP_TOP
# getattr(x, "attr")
3 7 LOAD_GLOBAL 1 (getattr)
10 LOAD_FAST 0 (x)
13 LOAD_CONST 1 ('attr')
16 CALL_FUNCTION 2
19 POP_TOP
# x.__getattribute__("attr")
4 20 LOAD_FAST 0 (x)
23 LOAD_ATTR 2 (__getattribute__)
26 LOAD_CONST 1 ('attr')
29 CALL_FUNCTION 1
32 POP_TOP
the LOAD_ATTR instruction uses a much faster code path to get at the
internal dictionary, while the getattr() and __getattribute__ forms needs
to do extra work to get to the actual attribute lookup.
> Nevertheless, the general impression remains that dicts *are* faster
> than objects, because attribute lookup uses dicts itself. Is that
> correct?
correct. once the interpreter gets to actually do the lookup, the performance
is identical (and the dictionary implementation is *extremely fast*). it's the
stuff
that needs to be done to get there that differs.
</F>
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