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.format vs. %

Ethan Furman ethan at stoneleaf.us
Tue Jan 3 15:00:23 EST 2012 
Neil Cerutti wrote:
> On 2012-01-03, Stefan Krah <stefan-usenet at bytereef.org> wrote:
>> Andrew Berg <bahamutzero8825 at gmail.com> wrote:
>>> To add my opinion on it, I find format() much more readable and easier
>>> to understand (with the exception of the {} {} {} {} syntax), and would
>>> love to see %-style formatting phased out.
>> For me the %-style is much more readable. Also, it is significantly
>> faster:
>>
>> $ ./python -m timeit -n 1000000 '"%s" % 7.928137192'
>> 1000000 loops, best of 3: 0.0164 usec per loop
> 
> I have done a little more investigating, and the above is
> arguably not fair. Python is interpolating that string at compile
> time, as far as I can tell. Pretty cool, and not possible with
> .format, but it's just regurgitating a string literal over and
> over, which isn't of much interest.
> 
> % is faster, but not by an order of magnitude.
> 
> On my machine:
> 
> C:\WINDOWS>python -m timeit -n 1000000 -s "n=7.92" "'%s' % n"
> 1000000 loops, best of 3: 0.965 usec per loop
> 
> C:\WINDOWS>python -m timeit -n 1000000 -s "n=7.92" "'{}'.format(n)"
> 1000000 loops, best of 3: 1.17 usec per loop
> 

Good information.  Thanks.

~Ethan~
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