[mapserver-users] MapScript import errors (Module not found) in Python venv with global install

[Seth G]

Hi Maëlle,

MapScript (and MapServer) use many of the same dependent DLLs as QGIS - GDAL, Proj, GEOS etc. which would then get loaded into memory by Python. 
For everything to work correctly, all these dependencies would have to be the same version, and (I think this is still the case), compiled with the same version of Microsoft Visual C (the 1928, 1931 etc. use when naming the GISInternals zips). 
It probably would be possible to get everything build and working, but you'd likely have to compile everything yourself. 
Is it possible to modify your workflow so a PyQGIS environment dumps out data to disk and then a MapScript environment works on this data? 
I'd imagine PyQGIS can probably do everything MapScript can, except for manipulate Mapfiles - you could take a look at mappyfile for this, which is Python only has has no dependent DLLs.

Seth

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On Thu, Apr 28, 2022, at 11:42 AM, maëlle lapriel wrote:
> I'm trying to write a PyQGIS standalone script which utilizes MapScript for certain tasks. In a first attempt, I basically did this:
> 
> - I installed MapScript globally with pip and using the Python 3.9.5 interpreter which ships with QGIS 3.22.6 (also includes wheel)
> - Created a venv with --system-site-packages
> - Downloaded the appropriate Windows binary build of MapServer from GISInternals (release-1928-x64-gdal-3-4-mapserver-7-6) and extracted into C:\MapServer\
> - Set the MAPSERVER_DLL_PATH to C:\MapServer\bin
> 
> However, whenever I try to load MapScript, it yields the following:
> 
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
>   File "C:\QGIS\apps\Python39\lib\site-packages\mapscript\__init__.py", line 2, in <module>
>     from .mapscript import *
>   File "C:\QGIS\apps\Python39\lib\site-packages\mapscript\mapscript.py", line 13, in <module>
>     from . import _mapscript
> ImportError: DLL load failed while importing _mapscript: The specified module could not be found.
> 
> As to where the README over at github indicates that this means MapServer.dll can't be found.
> 
> In order to rule out possible issues, I also tried the following:
> 
> - Not creating a venv, but using it with the QGIS python version directly
> - Installing MapScript into normal installations of python 3.7, 3.8, 3.9, 3.10
> - Using it together with the latest builds of MapServer (1930)
> - Not installing MapScript with pip but copying over mapscript.py and _mapscript.pyd from the respective MapServer builds
> - Adding C:\MapServer\bin to PATH instead of the new env variable
> 
> All with the same result. The only ever combination I got it working is when installing the MapScript globally using python3.6/pip and the old MapServer release-1911 (7.6.1), where I sadly can't import PyQGIS in the version I need.
> 
> What could be the issue here? 
> 
> Kind regards, Maëlle
> _______________________________________________
> MapServer-users mailing list
> MapServer-users at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/mapserver-users
> 
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