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<p class=MsoNormal><span lang=IS>Hello there.<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>I‘ve just noticed what I consider a
performance problem:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>Using new style classes to provide
attribute-like access using __getattr__ is considerably slower than old style
classes: Observe:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS><o:p> </o:p></span></p>
<p class=MsoNormal><span lang=IS>s = """<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>class dude:<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS> def bar(self):pass<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS> def __getattr__(self, a): return a <o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>class dude2(object):<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS> def bar(self):pass<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS> def __getattr__(self, a): return a <o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>d = dude()<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>d2 = dude2()<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>d.a = d2.a = 1<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>"""<o:p></o:p></span></p>
<p class=MsoNormal><span lang=IS>timeit.Timer(Žd.fooŽ, s).timeit()<o:p></o:p></span></p>
<p class=MsoNormal>>0.32979211801421116<o:p></o:p></p>
<p class=MsoNormal><span lang=IS>timeit.Timer(Žd2.fooŽ, s).timeit()<o:p></o:p></span></p>
<p class=MsoNormal>> 1.1119853719342245<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>The overhead is almost 3 times as high. I imagine that this
is because new style classes must search further and harder before giving up
and going to __getattr__.<o:p></o:p></p>
<p class=MsoNormal>For the bound method the difference is less:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=IS>timeit.Timer(Žd.barŽ, s).timeit()<o:p></o:p></span></p>
<p class=MsoNormal>> 0.11835480370018558<o:p></o:p></p>
<p class=MsoNormal><span lang=IS>timeit.Timer(Žd2.barŽ, s).timeit()<o:p></o:p></span></p>
<p class=MsoNormal>> 0.17820851929263881<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>For fun, I also tested regular attributes, and see:<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><span lang=IS>timeit.Timer(Žd.aŽ, s).timeit()<o:p></o:p></span></p>
<p class=MsoNormal>> 0.069161394202183146<o:p></o:p></p>
<p class=MsoNormal><span lang=IS>timeit.Timer(Žd2.aŽ, s).timeit()<o:p></o:p></span></p>
<p class=MsoNormal>> 0.17966275972594303<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>I’m surprised that accessing instance attributes like
this is twice as slow using new style classes.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Any thoughts on this?<o:p></o:p></p>
<p class=MsoNormal>We are using a lot of low-level attribute access magic in
EVE and so it would appear that we are best served by sticking with old-style
classes. But these are going away eventually, so what to do?<o:p></o:p></p>
<p class=MsoNormal>Where is this extra overhead coming from?<o:p></o:p></p>
<p class=MsoNormal>And oh, it is no use using __getattribute__ instead, since
it will always involve calls to object.__getattribute__ and become very slow.<o:p></o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Cheers,<o:p></o:p></p>
<p class=MsoNormal>Kristj<span lang=IS>án<o:p></o:p></span></p>
<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal><o:p> </o:p></p>
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