timeit.timeit and timeit.repeat give different answers

Dan Christensen jdc at uwo.ca
Tue Jul 13 19:05:00 CEST 2004


Can anyone confirm whether this discrepancy happens with other
installations of python on other hardware/OS's?  It's a bit
disconcerting. 

Thanks,

Dan

Dan Christensen <jdc at uwo.ca> writes:

> The test below is done with Python 2.4a1 compiled from source, but
> the same thing happens with Debian's python2.3_2.3.4-2.
>
> Python 2.4a1 (#1, Jul 11 2004, 12:20:32) 
> [GCC 3.3.4 (Debian)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>>>> import timeit
>>>> import time  
>>>> t=timeit.Timer("pass","pass",time.time)
>>>> print t.timeit()
> 0.0560228824615
>>>> print t.repeat(1)      
> [0.042751073837280273]
>
> The results are consistent if repeated, i.e. timeit always produces
> about 0.056 and repeat always produces about 0.043.
>
> It doesn't help to do:
>
>   for i in range(10):
>     print t.timeit()
>
> vs.
>
>   print t.repeat(10)
>
> The problem happens on both machines I've tested it on.  One is a
> desktop.  No other jobs running.
>
> With Python 2.3, the results are affected by the setting of the
> PYTHONPATH environment variable.  With it unset or set to an empty
> directory /tmp/foo I get results like above.  With it set to an empty
> directory /tmp/python, I get results that agree with each other.
>
> But with Python 2.4, all three settings give results that disagree.
>
> If I use the ipython shell, things are even worse:  the results
> disagree by a factor of almost 2!
>
> I've read timeit.py and can't see how this might happen.
>
> Any thoughts?
>
> Dan



More information about the Python-list mailing list