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

[Glenn Linderman]

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.

Glenn
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