[Python-Dev] PEP 364, Transitioning to the Py3K standard library

[Barry Warsaw]

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On Mar 7, 2007, at 5:46 PM, BJörn Lindqvist wrote:

>> When Python's import machinery is initialized, the oldlib package is
>> imported.  Inside oldlib there is a class called ``OldStdlibLoader``.
>> This class implements the PEP 302 interface and is automatically
>> instantiated, with zero arguments.  The constructor reads all the
>> ``.mv`` files from the oldlib package directory, automatically
>> registering all the remappings found in those ``.mv`` files.  This is
>> how the Python 2.x standard library is remapped.
>
> Will not reading all those .mv files add a lot of overhead? Disk seeks
> is not cheap.

I don't think so.  There will likely be just a few .mv files in the  
stdlib and they'd all get loaded at Python startup time.  A  
package's .mv file would only get loaded when the package gets  
imported.  Once read I don't think we'd need to stat for those or  
read them again.

It would definitely be worth measuring, but my guess is the  
additional overhead will be negligible.

- -Barry

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