[Python-Dev] New Windows installer for Python 3.5

Steve Dower Steve.Dower at microsoft.com
Mon Jan 5 19:14:27 CET 2015

Ethan Furman:
> On 01/04/2015 02:56 PM, Steve Dower wrote:
>> ChrisA wrote:
>>> You talk of installing by default into Program Files, and having a 
>>> separate per-user installation mode. How do these two installation 
>>> targets interact? Suppose someone installs 3.5 globally, then 
>>> installs
>>> 3.6 for self only? Or installs 3.5.1 for self only? I would normally 
>>> expect a per-user installation to trump a global one, but this could 
>>> make for a lovely dep-hell on a system that's used by one person, who 
>>> then isn't sure what was installed as admin and what wasn't.
>> Yeah, it gets a little messy, especially if you keep adding all the 
>> Python versions to PATH (Windows will always put per-user PATH entries 
>> at the end). The py.exe launcher handles this best, and the system 
>> version will always be found first.
> py.exe should *not* follow this behavior. User installs should be searched
> first, then system installs -- otherwise, what's the point in having a
> user-install? Filling up the gobs of disk-space we now have available?

Typo on my part. The py.exe launcher will always find the *user* install first. Searching PATH will always find the system version first.

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