I am trying to run a rastercalculator through a call to its python method and I
get the error message core.QgsProcessingException: An error occurred while
performing the calculation. Not a very intuitive message.
The variable _cutfill_nodata_file used in the code below is a path to a result
from a previous geoprocessing call and the file does exist, but the call to
rastercalculator seems to have an issue with that file. If I replace
_cutfill_nodata_file with
self._elevation_layer.dataProvider().dataSourceUri()}@1 it works. Not what I
want to do, but just wanted to test nothing odd about my expression. Do that
basically adds the same layer to itself so I am doubling the cell values. I
want to add the values in the file _cutfill_nodata_file, but when I use that
file, I get the error below. I tried using just the layer name and band which
is what is used in the GUI raster calculator, but that does not work and I
expect it to not as I think it only works if the layers are in the layer panel
which they are not, they are in a temp folder, so I am calling the method using
the file names.
elevation_30m_cutfill_file = os.path.join(self._temp_dir.name,
f"{self._elevation_layer.name()}_{self.cutfill_layer.name()}.tif")
elevation_30m_cutfill_name =
os.path.splitext(os.path.basename(elevation_30m_cutfill_file))[0]
expression = f'\"{self._elevation_layer.dataProvider().dataSourceUri()}@1\" +
\"{_cutfill_nodata_file}@1\"'
processing.run(
"qgis:rastercalculator",
{
'EXPRESSION':expression,
'LAYERS':[self._elevation_layer.dataProvider().dataSourceUri()],
'CELLSIZE':0,
'EXTENT':None,
'CRS':None,
'OUTPUT':elevation_30m_cutfill_file
}
)
File
"C:\Users\RDTECLAC\AppData\Roaming\QGIS\QGIS3\profiles\default\python\plugins\site_selection\tools\cutfill\cutfill_dialog.py",
line 745, in _calculate_cutfill_elevation_layer
processing.run(
File
"C:\PROGRA~1/QGIS31~1.16/apps/qgis-ltr/./python/plugins\processing\tools\general.py",
line 108, in run
return Processing.runAlgorithm(algOrName, parameters, onFinish,
feedback, context)
File
"C:\PROGRA~1/QGIS31~1.16/apps/qgis-ltr/./python/plugins\processing\core\Processing.py",
line 174, in runAlgorithm
ret, results = execute(alg, parameters, context, feedback,
catch_exceptions=False)
File
"C:\PROGRA~1/QGIS31~1.16/apps/qgis-ltr/./python/plugins\processing\gui\AlgorithmExecutor.py",
line 71, in execute
results, ok = alg.run(parameters, context, feedback, {}, False)
_core.QgsProcessingException: An error occurred while performing
the calculation
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