caching attribute reference

[micseydel]

@Ofnuts, given the advice at https://wiki.python.org/moin/PythonSpeed...iding_dots... and my inability to find anything saying that CPython does any kind of optimization, I'm really doubtful of that. PyPy very well could.

[wavic]

Numba?

[Ofnuts]

@Ofnuts, given the advice at https://wiki.python.org/moin/PythonSpeed...iding_dots... and my inability to find anything saying that CPython does any kind of optimization, I'm really doubtful of that. PyPy very well could.

OK, so some experimental evidence that you are right:

import timeit,random

class Counter(object):
    def __init__(self):
        self.someattribute=0
    
    def runAttrib1(self,runs):
        self.someattribute=0
        x=random.randint(1,10)
        for _ in range(runs):
            self.someattribute+=x
        return self.someattribute
            
    def runAttrib2(self,runs):
        self.someattribute=0
        x=random.randint(1,10)
        for _ in range(runs):
            self.someattribute=self.someattribute+x
        return self.someattribute
            
    def runLocal(self,runs):
        self.someattribute=0
        attribcopy=self.someattribute
        x=random.randint(1,10)
        for _ in range(runs):
            attribcopy+=x
        self.someattribute=attribcopy
        return x

counter=Counter()
number=1000
print ("%12s: %12.8f" % ('Attrib1',timeit.timeit(stmt='counter.runAttrib1(100000)',setup='from __main__ import counter', number=number)))
print ("%12s: %12.8f" % ('Attrib2',timeit.timeit(stmt='counter.runAttrib2(100000)',setup='from __main__ import counter', number=number)))
print ("%12s: %12.8f" % ('Local',  timeit.timeit(stmt='counter.runLocal(100000)',  setup='from __main__ import counter', number=number)))

Output for Python2:

Output:
     Attrib1:  10.37185884
     Attrib2:   8.38905406
       Local:   5.44241190

Output for Python3:

Output:
     Attrib1:   9.38220573
     Attrib2:   8.99003031
       Local:   4.89760979

So yes, some optimizations aren't done. Strangely var+=x (Attrib1) is slower than var=var+x (Attrib2)...

[Skaperen]

it's nice to know
just what is slow
that we may code
without much load