[QGIS-Developer] QGIS plugin depends on pypi package

[Julien Moura]

Hello John,


It's a recurring issue/question since QGIS does not support pip 
dependencies and that PyQGIS plugins are not following the official 
Python packaging standards from PEPs and related formats (typically 
metadata.txt instead of setup.cfg, pyproject.toml). You will find some 
unsuccessful QEPs about this. For example: 
https://github.com/qgis/QGIS-Enhancement-Proposals/issues/202.


Shortly, here come 3 workarounds:

  * basic: run pip install in a rough subcommand. Not so elegant but
    still efficient.
  * re-wheeling: implement a minimalist (or complete) 3rd party packages
    managers, miming pip through QgsNetwork tooling. Best example I know
    until today: ENMap-Box plugin (see attached screenshot or try it
    yourself).
  * YAML addicts: run your pip install during your plugin's packaging
    job in CI and include external dependencies in a subfolder before
    deploying it to your favorite plugins repository. Then, manage
    install loading from your plugin with try/except ImportError and
    'site' module. This is the way I prefer and use for years now. Main
    downside: for dependencies requiring a specific compilation on an
    operating system, you need to include various outputs. See Roof
    Classify <https://github.com/DINFO-UniFI/RoofClassify> (GitHub
    Workflow), Thyrsis <https://gitlab.com/Oslandia/qgis/thyrsis>
    (GitLab CI), QSoccer <https://gitlab.com/Oslandia/qgis/QSoccer/>
    (GitLab CI), QDuckDB <https://gitlab.com/Oslandia/qgis/qduckdb>
    (GitLab CI)... If you're interested, let me know. It could motivate
    me to write a tutorial detailing this method.
  * bravehearts: working on packaging your dependencies into osgeo4w;
    but they probably won't be included in default QGIS packages (.msi)

Just a quick advice: if you do some pip install within your plugin, 
during the packaging or during the run, make it under a custom folder 
related only to your plugin and use site to load extra dependencies in 
the QGIS Python environment to avoid issues.


Good luck!

Regards

Julien


Le 19/01/2024 à 19:16, John Lindsay via QGIS-Developer a écrit :
>
> Agreed, when I 'print(sys.executable)' from within the QGIS Python 
> Console (on my MacBook Pro), I see:
>
>
> /Applications/QGIS.app/Contents/MacOS/QGIS
>
>
> But from my system terminal, I see:
>
> /Library/Frameworks/Python.framework/Versions/3.11/bin/python3
>
>
> So QGIS, at least on a Mac, does seem to have it's own version of 
> Python installed. And there is not clear way, again on a Mac at least, 
> to pip install to the QGIS Python such that a plugin will be able to 
> see a package. Now, this said, on my Linux machine, installing my 
> Whitebox Workflows plugin did not run into an error at all and so I'm 
> left wondering if this is perhaps, as Greg suggested, a particular 
> binary distribution issue related to QGIS on MacOS. Could be.
>
> Regards,
>
> John
>
> Prof. John Lindsay
>
> Dept. of Geography, Environment & Geomatics,
>
> The University of Guelph,
>
> Room 122, Hutt Building,
>
> E-mail: jlindsay at uoguelph.ca
>
> Phone: (519) 824-4120 ext. 56074
>
> Web: https://geg.uoguelph.ca/faculty/lindsay-john
>
> Research page: https://jblindsay.github.io/ghrg/index.html
>
> WhiteboxTools GIS project: https://www.whiteboxgeo.com/
>
> Twitter: https://twitter.com/whiteboxgeo
>
> ------------------------------------------------------------------------
> *From:* David Strip <qgis-dev at stripfamily.net>
> *Sent:* Friday, January 19, 2024 1:10 PM
> *To:* Greg Troxel <gdt at lexort.com>; John Lindsay <jlindsay at uoguelph.ca>
> *Cc:* John Lindsay via QGIS-Developer <qgis-developer at lists.osgeo.org>
> *Subject:* Re: [QGIS-Developer] QGIS plugin depends on pypi package
> CAUTION: This email originated from outside of the University of 
> Guelph. Do not click links or open attachments unless you recognize 
> the sender and know the content is safe. If in doubt, forward 
> suspicious emails to IThelp at uoguelph.ca.
>
> On 1/19/2024 10:59 AM, Greg Troxel via QGIS-Developer wrote:
>> When you say "qgis seems to use its own version", I wonder if that is in
>> the context of particular binary distribution.  And if there really is a
>> full extra copy of libs, or if it's about a per-user site-packages
>> directory.
> The OS4Geo binary distribution contains a Python39 directory which is 
> a full python installation including python.exe, a Lib directory which 
> in turn contains a site-packages directory. As least in my case, this 
> is installed system-wide, not per-user
>
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