On 14/11/2012 10:11, mar...@v.loewis.de wrote:
Zitat von Chris Withers <ch...@simplistix.co.uk>:
a_dict = dict(
x = 1,
y = 2,
z = 3,
...
)
What can we do to speed up the former case?
It should be possible to special-case it. Rather than creating
a new dictionary from scratch, one could try to have the new dictionary
the same size as the original one, and copy all entries.
Indeed, Doug, what are your views on this? Also, did you have a
real-world example where this speed difference was causing you a problem?
I don't know how much this would gain, though. You still have to
create two dictionary objects. For a better speedup, try
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
For the naive observer (ie: me!), why is that?
Chris
--
Simplistix - Content Management, Batch Processing & Python Consulting
- http://www.simplistix.co.uk
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