shared lib from python code?

Diez B. Roggisch deets at nospam.web.de
Mon Feb 23 14:10:49 CET 2009


Gabriel Rossetti schrieb:
> Gabriel Rossetti wrote:
>> Hello everyone,
>>
>> I would like to know if it is possible to turn python code into a 
>> shared lib? I have several processes that use the same base code, and 
>> it seems like every process loads the "shared" code into memory. I 
>> would like it to be loaded once and shared, like a .so in linux or a 
>> .dll in windows and have the interpreters use the dared copy. Is there 
>> a way to do this?
>>
>> Thank you,
>> Gabriel
>>
> Ok, maybe I mis-stated my problem (or mis-understood your answers).. I 
> don' t want to share code as in have multiple processes access a 
> variable and have the same value, like it is done in threads, what I 
> want is to not have n copies of the code (classes, functions, etc) 
> loaded by n python interpreters. When you load Apache for instance, it 
> runs n processes but loads only one copy of parts of it's code (so/dll), 
> that's what I want to do. In C/C++ I would write a shared-lib (so/dll), 
> so once the system has loaded it, it doesn' t re-load it when another 
> process needs it.

This is not done, and most probably won't ever happen. What would you do 
with this?

import random
import foo


if random.random() > .5:
    foo.some_function = lambda x: x ** 2
else:
    foo.some_function = lambda x: x + 2


If the module foo would be shared amongst processes, these would affect 
the code of each other. Not so nice.

Of course one could try & cough up some read-only, copy-on-modify 
scheme, but that would be hard, if not impossible - and for rather 
minimal gains. Take a look at the compiled *.pyc-files (which should 
pretty much represent the memory they consume) - they are in the kbytes. 
So optimizing here would be a waste I'd say.


Diez



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