[SciPy-dev] time to import scipy?

David Cournapeau david@ar.media.kyoto-u.ac...
Tue Mar 11 21:30:45 CDT 2008

Joseph VanAndel wrote:
> When I import scipy (or just scipy.io) on a CentOS 5 64 bit computer, 4 
> processor, 3.00 Ghz server, with Python 2.5.1, it takes ~10 seconds of 
> elapsed time.
> When I'm developing and testing a Python script, I typically start the 
> python interpreter dozens of times, so I concerned by how much time I 
> spend waiting for the Python to startup.
> 1) Is there anything I can do to speed up the import of scipy?

Where is scipy (and its dependencies) installed ? Is it on NFS (or slow 
filesystem, usb, etc...) ? If so, putting it locally could be a huge win.

10 second for scipy the first time (cold start) is not surprising: scipy 
is a big package, and most time is spent on IO (reading files from the 
fs). But the 2d time, a lot of this is in memory (IO buffer), so it will 
be very fast. Numbers given by Ondrej suggest that it is a hot start in 
his case (or that he has an extremely powerful workstation:) ).

In my case (and scipy is on NFS):

(cold start)
time python -c "import scipy"

real    0m4.007s
user    0m0.440s
sys     0m0.236s

(hot start)
time python -c "import scipy"

real    0m0.867s
user    0m0.388s
sys     0m0.212s

> 2) What debugging techniques do you  suggest that avoid restarting the 
> interpreter?  For example, do you routinely use ipython and 
> reload(my_module)
It depends on the situation. If you are debugging one script, ipython 
has the %run method for that. But if you need to modify several modules 
which import each other, it becomes tricky.



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