On 4/18/2025 11:38 AM, Peter J. Holzer via Python-list wrote:
On 2025-04-18 13:24:28 +1200, Greg Ewing via Python-list wrote:
On 18/04/25 9:41 am, Mats Wichmann wrote:
There's just not a really great answer to this.
Seems to me a system-installed application shouldn't be looking in the
user's .local packages in the first place. That should only be for things
the user has installed "for this user".
It's not the application that looks into .local, it's Python. If you say
that a system-installed Python shouldn't look into ~/.local, then you've
just disabled that mechanism completely. If not then Python would
somehow have to distinguish between system-installed and user-installed
scripts. This isn't as easy as checking whether the path starts with
/usr/bin or whether it belongs to root. Tying into the system's package
manager doesn't look appealing to me (not to mention that it might be
unacceptably slow).
Let's try a specific example. Let's say that PyQt6 v6.8.3 is installed
in the system site directory. The OS uses PyQt6 for some system
purposes. Now the user comes along and forces an install of PyQt6 v6.9.0
in the user site directory. 6.9.0 has a bug that would crash one of the
system's application but not the user's programs. (This is not a
far-fetched scenario).
When the system launches its application the PYTHONPATH will start with
system site directories; local user site directories will be on the
PYTHONPATH but since they come later, the python will use PyQt6 v6.8.3
because that will come first on the path. No crash here.
If the user has a program that actually does require the use of v6.9.0,
he's going to have to make sure that the user's local site directories
come first on the path. One way to do that is to set the PYTHONPATH to
point to the user's location.
In what scenario is a system application going to load a wrong version
of a dependency from a user's site location? The only one I can think of
is for the user, with the help of sudo, or by editing some
system-enabled script, were to change the global PYTHONPATH. That seems
a stretch.
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