I'm trying to create a script which takes an unkown number of equal size rasters and returns a single raster identifying the source (raster) of the maximum value for each pixel. GDAL is telling me it cannnot find a file when I call it from a script in the QGIS processing script editor.

My script that is generating the error is below, specifically, when it calls UpdateTocRaster:

class FindTimeOfConcentration(QgsProcessingAlgorithm):

    def initAlgorithm(self, config=None):
        self.addParameter(QgsProcessingParameterMultipleLayers('waterlevelgrids', 'Water level grids', layerType=QgsProcessing.TypeRaster, defaultValue=None))

    def processAlgorithm(self, parameters, context, model_feedback):
        # Use a multi-step feedback, so that individual child algorithm progress reports are adjusted for the
        # overall progress through the model
        feedback = QgsProcessingMultiStepFeedback(5, model_feedback)
        results = {}
        outputs = {}
        layers = self.parameterAsLayerList(parameters, 'waterlevelgrids', context)
        max_raster = layers[0]
        toc_raster = self.initiateRasterID(max_raster, context, feedback)['OUTPUT']
        for count, layer in enumerate(layers[1:]):
            feedback.pushInfo(f'Processing raster {count}')
            feedback.pushInfo(f'Updating time of concentration raster')
            toc_raster = self.updateTocRaster(toc_raster, max_raster, layer, count+2, context, feedback)['OUTPUT']
            feedback.pushInfo(f'Updating max raster')
            max_raster = self.updateMaxRaster(max_raster, layer, context, feedback)['OUTPUT']
        return results

the function updateTocRaster looks like:

def updateTocRaster(self, toc_raster, max_raster, layer, count, context, feedback):
    alg_params = {
        'BAND_A': 1,
        'BAND_B': 1,
        'BAND_C': None,
        'BAND_D': None,
        'BAND_E': None,
        'BAND_F': None,
        'EXTRA': '',
        'FORMULA': f'(A>=B)*C+(A<B)*{count}',
        'INPUT_A': max_raster,
        'INPUT_B': layer,
        'INPUT_C': toc_raster,
        'INPUT_D': None,
        'INPUT_E': None,
        'INPUT_F': None,
        'NO_DATA': None,
        'OPTIONS': '',
        'RTYPE': 5,  # Float32
        'OUTPUT': QgsProcessing.TEMPORARY_OUTPUT
    return processing.run('gdal:rastercalculator', alg_params, context=context, feedback=feedback, is_child_algorithm=True)

The log shows this error but I can load the files using the filepaths below for A, B and C. I cannot load the outfile but I assume that is because it is not created:

Processing raster 0
Updating time of concentration raster
GDAL command:
gdal_calc.bat --overwrite --calc "(A>=B)*C+(A<B)*2" --format GTiff --type Float32 -A "J:/2_Invercargill Jobs/S01500-S01599/S01555_Riverton/300_Riverton_Model/006_Design/Tuflow/2_Model/results/2d/Grids/RIV_001_100yr+1HR+T20SLR300_8m_d_g001_Max.asc" --A_band 1 -B "J:/2_Invercargill Jobs/S01500-S01599/S01555_Riverton/300_Riverton_Model/006_Design/Tuflow/2_Model/results/2d/Grids/RIV_001_100yr+2HR+T20SLR300_8m_d_g001_Max.asc" --B_band 1 -C C:/Users/chcgis/AppData/Local/Temp/processing_SQFrqz/133e2c3a47ca490d91bd8edca7c05376/OUTPUT.tif --outfile C:/Users/chcgis/AppData/Local/Temp/processing_SQFrqz/037f8b08b5a248f08d8fc0203e0137a4/OUTPUT.tif
GDAL command output:
The filename, directory name, or volume label syntax is incorrect.
Process returned error code 1
  • 2
    Test if it works from a path without spaces ...2_Invercargill Jobs...
    – user30184
    Apr 11, 2022 at 11:01
  • No luck, still get the same error: GDAL command output: The filename, directory name, or volume label syntax is incorrect. Process returned error code 1 Apr 11, 2022 at 21:50

1 Answer 1


Not really an answer but I ended up switching to using the grass calculator (r.mapcalc.simple) which worked just fine

def updateTocRaster(self, toc_raster, max_raster, layer, count, context, feedback):
    # r.mapcalc.simple
    alg_params = {
        'a': max_raster,
        'b': layer,
        'c': toc_raster,
        'd': None,
        'e': None,
        'expression': f'(A>=B)*C+(B<A)*{count}',
        'f': None,
        'output': QgsProcessing.TEMPORARY_OUTPUT
    return processing.run('grass7:r.mapcalc.simple', alg_params, context=context, feedback=feedback, is_child_algorithm=True)

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