[Numpy-discussion] slow import of numpy modules

Michael McNeil Forbes mforbes@physics.ubc...
Wed Jul 2 19:00:24 CDT 2008

On 2 Jul 2008, at 3:59 PM, Robert Kern wrote:
> On Wed, Jul 2, 2008 at 17:43, Nathan Jensen  
> <Nathan_Jensen@raytheon.com> wrote:
>> Hi,
>> I was wondering if there was any way to speed up the global import of
>> numpy modules.  For a simple import numpy, it takes ~250 ms.  In
>> comparison, importing Numeric is only taking 40 ms.  It appears that
>> even if you only import a numpy submodule, it loads all the  
>> libraries,
>> resulting in the painful performance hit.  Are there plans to  
>> speed up
>> the importing of numpy,
> I am not sure how much is possible.
>> or at least have it not load libraries that
>> aren't requested?
> At this point in time, it is too late to make such sweeping changes  
> to the API.

One could use an environmental variable such as  
NUMPY_SUPPRESS_TOP_LEVEL_IMPORTS, that, if defined, suppresses the  
importing of unneeded packages.  This would only affect systems that  
define this variable, thus not breaking the API but providing the  
flexibility for those that need it.  (This or a similar variable  
could also contain a list of the numpy components to import  

If you want to try this, just modify numpy/__init__.py with something  
like the following

     import os
     fast_import = if 'NUMPY_SUPPRESS_TOL_LEVEL_IMPORTS' in os.environ
     del os

     if fast_import:
         <customised imports>
         <standard imports etc.>

     del fast_import


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