[Python-Dev] PEP 405 (pyvenv) and system Python upgrades (original) (raw)

Glenn Linderman v+python at g.nevcal.com
Sat May 5 05:58:25 CEST 2012

On 5/4/2012 8:48 PM, Terry Reedy wrote:

CPython is developed, tested, packaged, distributed, and installed as one unit. It is intended to be run as one package. If something caches a copy of python.exe, it seems to me that it should check and update as needed. Could venv check the file date of the current python.exe versus that of the one cached, much like is done with .pyc compiled code caches?

I almost wrote this response (using different words, but the same idea) but concluded that:

  1. Python wouldn't run far without its standard library, so a venv check would have to be very early, and likely coded in C, and therefore probably has to be part of Python.exe

  2. If it was not part of Python.exe, it would have to work similarly to the launcher, and there would be yet one more process sitting around waiting for Python to exit (on Windows, where there is no exec).

So I concluded that probably Python.exe needs to make the check, but if it is aware it existing in venv, it might be able to put out a better message than "just" the mismatch between exe and lib; or at least the message should mention the possibility of an old venv cache.

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