[Python-Dev] PEP 364, Transitioning to the Py3K standard library (original) (raw)

Barry Warsaw barry at python.org
Thu Mar 8 00:45:10 CET 2007

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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.

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