Performance Tracker project update

Ivan Voras ivoras at
Fri Feb 8 19:42:16 UTC 2008

Brooks Davis wrote:
> On Fri, Feb 08, 2008 at 09:41:09AM +0100, Erik Cederstrand wrote:
>> I finally got around to testing this, and with a combination of mtree 
>> comparing md5 hashes, bsdiff compacting changed files and hardlinking 
>> unchanged files I get a reduction in size from 256MB to 10MB. Pretty good, 
>> and the whole operation only takes a few minutes.
> Cool!
>> I have one peculiarity, though. I install python2.5 into the directory 
>> containing the build, and even though the python version has not changed, I 
>> still get mismatching md5 sums on every .pyo and .pyc file. Any thoughts on 
>> this?
> I'm not a python guru by any means, but I think .pyc files probably have data
> about the .py they are generated from because there's some sort of
> auto-generation available.  It may be possible to not store them at all and
> just generate them before you use them or add some magic build flags to cause
> them to store some sort of cooked values.  I'm not sure where the .pyo files
> come from.

.pyc/.pyo contain at least the timestamp of the original .py file and 
maybe a compilation timestamp. You can indeed safely delete all .pyc and 
.pyo files and forget about them - the only penalty will be slightly 
slower application startup times as the .py files are compiled every time.

.pyo are optimized version of .pyc. AFAIK currently the optimizations 
are not worth it.

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