[Qgis-user] 3.16.8+ LTR vs. old 3.16.x for SIP and PyQt5 imports

[Ari Meyer]

Hi,

I mistakenly posted this to the Nabble list just before it got shut down.

I wrote (adding some specifics):
There were clearly major changes in 3.16.8+ LTR compared with the older
3.16.x and 3.18.y (apparently to bring it in line with 3.20+).  We have had
problems with the new LTR versions when attempting to import SIP and
PyQt5.  Everything else seems to work fine, at least so far.
V2 installer:
* Desktop
* qgis-ltr 3.16.9-1
* saga: SAGA
* Libs
* qgis-ltr-grass-plugin
* python3-geopandas
* python3-pip
* python3-scipy
* python3-setuptools

Test with python-qgis-ltr.bat:
Python 3.9.5 (tags/v3.9.5:0a7dcbd, May  3 2021, 17:27:52) [MSC v.1928 64
bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import sip
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ModuleNotFoundError: No module named 'sip'
>>> import PyQt5
>>> from PyQt5.QtWidgets import QHBoxLayout, QLabel, QPushButton,
QTreeWidgetItem, QWidget
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ImportError: DLL load failed while importing QtWidgets: The specified
module could not be found.
>>>

With 3.16.3, for instance, we don't see these errors.  I have tried to
trace through everything in the old and new versions, but can't seem to
identify the problem with 3.16 LTR.  Any ideas?  Is this a problem
specifically with the Windows DLLs, or are users on other platforms
experiencing similar problems?


Andrea Giudiceandrea responded:
I think the changes are not in QGIS itself, but in the new versions of the
dependencies installed with the new installer.
If you need to use previous dependencies, then you need to install QGIS
using the installers from from the "old OSGeo4W" repository.


I replied:
It doesn't appear to be merely a difference in dependency versions -- I
can't reference these dependencies at all now.  SIP and PyQt5 must be
included with QGIS 3.16.9 LTR, as our plugin code runs fine within it, but
I now can't import them from outside QGIS via the included
python-qgis-ltr.bat script, though, as shown, it works fine when using the
python-qgis.bat in the old 3.16.3.  Am I missing something?


He responded:
I think the issue is not in QGIS 3.16.9 itself, compared with QGIS 3.16.3.
It seems the issue is in the packaging of QGIS and its dependencies within
the new (v2/msi) OSGeo4W repository, while there is no issue with the old
(v1/exe) OSGeo4W repository.
QGIS 3.16.9 LTR is also available, with old packaging dependencies, using
the old OSGeo4W installer. Have you tried it?



So I tried with the V1 installer.  I installed with *essentially* the same
options:
- not sure about the GRASS plugin: common or 7? -- I picked common
- there are different versions of various dependencies between V1 and V2,
as expected

In any case, with the V1 install of 3.16.9 LTR, at least SIP/PyQt5 imported
fine.  One big difference I could immediately see, though, is that it
installed Python 3.7.0 instead of 3.9.5, which is usable, but 3.9 would
definitely be preferable.  I am concerned that if we stuck with V1 that we
wouldn't be supported to the same degree -- not sure if that's unwarranted.

I do believe, though, that the problems we are seeing after installing
qgis-ltr 3.16.9-1 with the V2 installer indicate some problem with the
installation and the python-qgis-ltr.bat environment config.  Is there
something else I need to do to get it to work?

Thanks,
Ari
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