I'm trying to connect to a PostgreSQL 13 database from PyQt/PySide.
When I get to con = QSqlDatabase.addDatabase('QPSQL'), I get the following console output:
QSqlDatabase: QPSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QPSQL
The second line, as far as I can tell, shows the QPSQL driver is found, but for some reason it's not loading.
I've scoured the internet, and tried copying DLLs around the place, as well as adding various directories to my system PATH, but haven't found a solution.
I've tried PyQt5, PyQt6, PySide2, and PySide6, all in fresh venvs, all have had the same issue. If I simply change the driver string to "QSQLITE", the driver loads successfully (though, obviously, the script subsequently runs into errors, as I'm not using SQLite).
I tried this on two Win10 machines and a Win7 machine, all had the same issue, though when I tried it on my Mac, it worked first try, no fiddling required.
I can't for the life of me figure out what's going on! Any help would be greatly appreciated.
EDIT: Extra info
I thought I'd fixed the problem by running as administrator (Win7), but then I ran into the same problem on Win10. I eventually got Win10 working, I think by running inside the venv I'd setup on the 7 machine for the script (though I had already tried that before, and tried a handful of other things, and it seemed to just "come good" all of a sudden rather than as a result of any one change - deactivating the venv definitely broke things, though)
So, now my script was working on a Win7 and Win10 machine, from the same venv - yay! I went on to try a further Win7 machine, and the error is back. I'm using the same venv on that machine.
To add to the confusion, I though I'd see what happened if I tried pyinstaller-ing the script on the "good" Win7 machine, then running it on the "bad". I couldn't get my .exe to run on the "good" machine until I copied the "platforms" and "sqldrivers" from the PyQt plugins folder to the .exe's folder. To me, this indicates that the .exe is looking in it's own directory for the libraries, and so should now work anywhere - unfortunatly, when I swap to the "bad" machine, I run into the same old error. I can force this error on the "good" machine by removing the "sqldrivers" folder from the .exe path, so it seems at least on that machine it really IS looking there.
There are copies of the "missing" .dll in every conceivable location, available to the OS and the script, I just can't figure out why it's sometimes not found!