[Python-Dev] performance of {} versus dict(), de fmd(**kw): return kw trumps all ; -)

[Xavier Morel]

On 2012-11-14, at 23:43 , Chris Withers wrote:

> On 14/11/2012 22:37, Chris Withers wrote:
>> On 14/11/2012 10:11, martin at v.loewis.de wrote:
>>> def xdict(**kwds):
>>>   return kwds
>> 
>> Hah, good call, this trumps both of the other options:
>> 
>> $ python2.7 -m timeit -n 1000000 -r 5 -v
>> "{'a':1,'b':2,'c':3,'d':4,'e':5,'f':6,'g':7}"
>> raw times: 1.45 1.45 1.44 1.45 1.45
>> 1000000 loops, best of 5: 1.44 usec per loop
>> $ python2.6 -m timeit -n 1000000 -r 5 -v
>> 'dict(a=1,b=2,c=3,d=4,e=5,f=6,g=7)'
>> raw times: 2.37 2.36 2.36 2.37 2.37
>> 1000000 loops, best of 5: 2.36 usec per loop$ python2.6 -m timeit -n
>> 1000000 -r 5 -v 'def md(**kw): return kw; md(a=1,b=2,c=3,d=4,e=5,f=6,g=7)'
>> raw times: 0.548 0.533 0.55 0.577 0.539
>> 1000000 loops, best of 5: 0.533 usec per loop
> 
> Before anyone shoots me, yes, wrong python for two of them:
> 
> $ python2.7 -m timeit -n 1000000 -r 5 -v "{'a':1,'b':2,'c':3,'d':4,'e':5,'f':6,'g':7}"
> raw times: 1.49 1.49 1.5 1.49 1.48
> 1000000 loops, best of 5: 1.48 usec per loop
> 
> $ python2.7 -m timeit -n 1000000 -r 5 -v 'dict(a=1,b=2,c=3,d=4,e=5,f=6,g=7)'
> raw times: 2.35 2.36 2.41 2.42 2.35
> 1000000 loops, best of 5: 2.35 usec per loop
> 
> $ python2.7 -m timeit -n 1000000 -r 5 -v 'def md(**kw): return kw; md(a=1,b=2,c=3,d=4,e=5,f=6,g=7)'
> raw times: 0.507 0.515 0.516 0.529 0.524
> 1000000 loops, best of 5: 0.507 usec per loop

The last one is kind-of weird, it seems to be greatly advantaged by the local lookup:

> python2.7 -m timeit -n 1000000 -r 5 -v "{'a':1,'b':2,'c':3,'d':4,'e':5,'f':6,'g':7}"                 
raw times: 0.676 0.683 0.682 0.698 0.691
1000000 loops, best of 5: 0.676 usec per loop
> python2.7 -m timeit -n 1000000 -r 5 -v 'dict(a=1,b=2,c=3,d=4,e=5,f=6,g=7)'                           
raw times: 1.64 1.66 1.4 1.44 1.44
1000000 loops, best of 5: 1.4 usec per loop
> python2.7 -m timeit -n 1000000 -r 5 -v 'def md(**kw): return kw; md(a=1,b=2,c=3,d=4,e=5,f=6,g=7)'    
raw times: 0.188 0.203 0.201 0.195 0.202
1000000 loops, best of 5: 0.188 usec per loop
> python2.7 -m timeit -n 1000000 -r 5 -v -s 'def md(**kw): return kw' 'md(a=1,b=2,c=3,d=4,e=5,f=6,g=7)'
raw times: 0.871 0.864 0.863 0.889 0.871
1000000 loops, best of 5: 0.863 usec per loop