percent faster than format()? (was: Re: optomizations)
Am 23.04.2013 06:00, schrieb Steven D'Aprano: If it comes down to micro-optimizations to shave a few microseconds off, consider using string % formatting rather than the format method. Why? I don't see any obvious difference between the two... Greetings! Uli -- http://mail.python.org/mailman/listinfo/python-list
Re: percent faster than format()? (was: Re: optomizations)
On Tue, Apr 23, 2013 at 9:46 AM, Ulrich Eckhardt
wrote:
> Am 23.04.2013 06:00, schrieb Steven D'Aprano:
>>
>> If it comes down to micro-optimizations to shave a few microseconds off,
>> consider using string % formatting rather than the format method.
>
>
> Why? I don't see any obvious difference between the two...
>
>
> Greetings!
>
> Uli
>
> --
> http://mail.python.org/mailman/listinfo/python-list
$ python -m timeit "a = '{0} {1} {2}'.format(1, 2, 42)"
100 loops, best of 3: 0.824 usec per loop
$ python -m timeit "a = '%s %s %s' % (1, 2, 42)"
1000 loops, best of 3: 0.0286 usec per loop
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Re: percent faster than format()? (was: Re: optomizations)
On Tue, 23 Apr 2013 09:46:53 +0200, Ulrich Eckhardt wrote:
> Am 23.04.2013 06:00, schrieb Steven D'Aprano:
>> If it comes down to micro-optimizations to shave a few microseconds
>> off, consider using string % formatting rather than the format method.
>
> Why? I don't see any obvious difference between the two...
Possibly the state of the art has changed since then, but some years ago
% formatting was slightly faster than the format method. Let's try it and
see:
# Using Python 3.3.
py> from timeit import Timer
py> setup = "a = 'spam'; b = 'ham'; c = 'eggs'"
py> t1 = Timer("'%s, %s and %s for breakfast' % (a, b, c)", setup)
py> t2 = Timer("'{}, {} and {} for breakfast'.format(a, b, c)", setup)
py> print(min(t1.repeat()))
0.8319804421626031
py> print(min(t2.repeat()))
1.2395259491167963
Looks like the format method is about 50% slower.
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Re: percent faster than format()? (was: Re: optomizations)
On Wed, Apr 24, 2013 at 12:36 AM, Steven D'Aprano
wrote:
> # Using Python 3.3.
>
> py> from timeit import Timer
> py> setup = "a = 'spam'; b = 'ham'; c = 'eggs'"
> py> t1 = Timer("'%s, %s and %s for breakfast' % (a, b, c)", setup)
> py> t2 = Timer("'{}, {} and {} for breakfast'.format(a, b, c)", setup)
> py> print(min(t1.repeat()))
> 0.8319804421626031
> py> print(min(t2.repeat()))
> 1.2395259491167963
>
>
> Looks like the format method is about 50% slower.
Figures on my hardware are (naturally) different, with a similar (but
slightly more pronounced) difference:
>>> sys.version
'3.3.0 (v3.3.0:bd8afb90ebf2, Sep 29 2012, 10:55:48) [MSC v.1600 32 bit (Intel)]'
>>> print(min(t1.repeat()))
1.4841416995735415
>>> print(min(t2.repeat()))
2.5459869899666074
>>> t3 = Timer("a+', '+b+' and '+c+' for breakfast'", setup)
>>> print(min(t3.repeat()))
1.5707538248576327
>>> t4 = Timer("''.join([a, ', ', b, ' and ', c, ' for breakfast'])", setup)
>>> print(min(t4.repeat()))
1.5026834416105999
So on the face of it, format() is slower than everything else by a
good margin... until you note that repeat() is doing one million
iterations, so those figures are effectively in microseconds. Yeah, I
think I can handle a couple of microseconds.
ChrisA
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