"optimizing out" getattr

[Daishi Harada]

Hi,

I'd like to get the 'get2' function below to
perform like the 'get1' function (I've included
timeit.py results).

I'm not sure how to write 'mkget' to do achieve
this, however, except to use 'exec' - is that what
would be necessary?

Thanks in advance,
d

---
class A:
a = 1
b = 2
a = A()
labels = ('a', 'b')
def get1(x):
return (x.a, x.b)
def mkget(attrs):
def getter(x):
return tuple(getattr(x , label) for label in attrs)
return getter
get2 = mkget(labels)

# % timeit.py -s "import test" "test.get1(test .a)"
# 1000000 loops, best of 3: 0.966 usec per loop
# % timeit.py -s "import test" "test.get2(test .a)"
# 100000 loops, best of 3: 4.46 usec per loop
---

[Stephen Thorne]

Re: "optimizin g out" getattr

On 14 Sep 2005 19:46:44 -0700, Daishi Harada <daishi@gmail.c om> wrote:[color=blue]
> Hi,
>
> I'd like to get the 'get2' function below to
> perform like the 'get1' function (I've included
> timeit.py results).[/color]

Do you have profiling results that show that a significant percentage
of your programs time is being spent inside this function?

If you don't, then you're wasting your time doing unnecessery optimisation.
--
Stephen Thorne
Development Engineer

[Peter Otten]

Re: &quot;optimizin g out&quot; getattr

Daishi Harada wrote:
[color=blue]
> I'd like to get the 'get2' function below to
> perform like the 'get1' function (I've included
> timeit.py results).[/color]
[color=blue]
> labels = ('a', 'b')
> def get1(x):
> return (x.a, x.b)
> def mkget(attrs):
> def getter(x):
> return tuple(getattr(x , label) for label in attrs)
> return getter
> get2 = mkget(labels)
>
> # % timeit.py -s "import test" "test.get1(test .a)"
> # 1000000 loops, best of 3: 0.966 usec per loop
> # % timeit.py -s "import test" "test.get2(test .a)"
> # 100000 loops, best of 3: 4.46 usec per loop[/color]
[color=blue]
> I'm not sure how to write 'mkget' to do achieve
> this, however, except to use 'exec' - is that what
> would be necessary?[/color]

No, you can just sit back and wait -- for Python 2.5:

$ cat attr_tuple25.py
import operator

class A:
a = 1
b = 2

get2 = operator.attrge tter("a", "b")

def get1(x):
return x.a, x.b

$ python2.5 -m timeit -s'from attr_tuple25 import A, get1, get2' 'get1(A)'
1000000 loops, best of 3: 0.813 usec per loop
$ python2.5 -m timeit -s'from attr_tuple25 import A, get1, get2' 'get2(A)'
1000000 loops, best of 3: 0.495 usec per loop

Time till release is not included in the timings :-)

Peter

[Kent Johnson]

Re: &quot;optimizin g out&quot; getattr

Peter Otten wrote:[color=blue]
> Daishi Harada wrote:
>
>[color=green]
>>I'd like to get the 'get2' function below to
>>perform like the 'get1' function (I've included
>>timeit.py results).[/color]
>
>
>[color=green]
>>labels = ('a', 'b')
>>def get1(x):
>> return (x.a, x.b)
>>def mkget(attrs):
>> def getter(x):
>> return tuple(getattr(x , label) for label in attrs)
>> return getter
>>get2 = mkget(labels)
>>
>># % timeit.py -s "import test" "test.get1(test .a)"
>># 1000000 loops, best of 3: 0.966 usec per loop
>># % timeit.py -s "import test" "test.get2(test .a)"
>># 100000 loops, best of 3: 4.46 usec per loop[/color]
>
> No, you can just sit back and wait -- for Python 2.5:
>
> $ cat attr_tuple25.py
> import operator
>
> class A:
> a = 1
> b = 2
>
> get2 = operator.attrge tter("a", "b")
>
> def get1(x):
> return x.a, x.b
>
> $ python2.5 -m timeit -s'from attr_tuple25 import A, get1, get2' 'get1(A)'
> 1000000 loops, best of 3: 0.813 usec per loop
> $ python2.5 -m timeit -s'from attr_tuple25 import A, get1, get2' 'get2(A)'
> 1000000 loops, best of 3: 0.495 usec per loop[/color]

With Python 2.4 you can at least get closer to the hardcoded version:

F:\>type attr_tuple.py
import operator

class A:
a = 1
b = 2

getA = operator.attrge tter("a")
getB = operator.attrge tter("b")

def get2(x):
return getA(x), getB(x)

def get1(x):
return x.a, x.b

F:\>python -m timeit -s"from attr_tuple import A, get1, get2" "get1(A)"
1000000 loops, best of 3: 0.658 usec per loop

F:\>python -m timeit -s"from attr_tuple import A, get1, get2" "get2(A)"
1000000 loops, best of 3: 1.04 usec per loop

Kent

[Daishi Harada]

Re: &quot;optimizin g out&quot; getattr

Peter Otten wrote:[color=blue]
> No, you can just sit back and wait -- for Python 2.5:[/color]

Thanks for the tip;
Although for my current use
I can't target 2.5, I hadn't even
noticed the attr/itemgetter
additions to operator in 2.4,
so I appreciate the pointer
for future reference.
d
[color=blue]
> $ cat attr_tuple25.py
> import operator
>
> class A:
> a = 1
> b = 2
>
> get2 = operator.attrge tter("a", "b")
>
> def get1(x):
> return x.a, x.b
>
> $ python2.5 -m timeit -s'from attr_tuple25 import A, get1, get2' 'get1(A)'
> 1000000 loops, best of 3: 0.813 usec per loop
> $ python2.5 -m timeit -s'from attr_tuple25 import A, get1, get2' 'get2(A)'
> 1000000 loops, best of 3: 0.495 usec per loop
>
> Time till release is not included in the timings :-)
>
> Peter[/color]

[jepler@unpythonic.net]

Re: &quot;optimizin g out&quot; getattr

If you are including C extensions, why not crib 2.5's implementation of
operator.attrge tter? It looks like it is fairly modular.

http://cvs.sourceforge.net/viewcvs.py/python/python/dist/src/Modules/operator.c

Jeff

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