4. FAILURE DIAGNOSIS
4. FAILURE DIAGNOSIS
| Error | Cause | Fix |
|---|---|---|
Layer is not valid |
Wrong path, unsupported driver, malformed file | Check path; verify with ogrinfo; inspect CRS |
QgsApplication not initialized |
Missing initQgis() call |
Call qgs.initQgis() before any QGIS operation |
QGIS prefix path not set |
Missing env setup | Set QgsApplication.setPrefixPath("/usr", True) or use default |
No module named 'qgis' |
QGIS Python not on PYTHONPATH | Run inside QGIS Python console or set PYTHONPATH |
CRS is not valid / unknown |
EPSG code not found | Use QgsCoordinateReferenceSystem.fromEpsgId(4326) |
Processing OUTPUT is None |
Algorithm failed silently | Check feedback.pushWarning() output; validate inputs |
offscreen platform error |
Qt platform missing | Install libqt5gui5; set QT_QPA_PLATFORM=offscreen |
| Shapefile truncated field names | Shapefile 10-char limit | Export to GeoPackage instead |