I'm batch dissolving some layers in QGIS and want to save each dissolved shapefile as <layername>_dissolved.shp. I'm using a for-loop but it just shows raise QgsProcessingException(msg) _core.QgsProcessingException: There were errors executing the algorithm. error.

Here's my code:

import processing
layers = QgsProject.instance().mapLayers().values()
for i in layers:
                   {'INPUT': i,
                    'OUTPUT': r'C:\Users\imper\Desktop\\' + str(i) + '_dissolved' + '.shp'})
    iface.addVectorLayer(str(i+_dissolved), '', 'ogr')

How should I revise my 'OUTPUT' file path?

  • 1
    Try os.path.join(r'C:\Users\imper\Desktop', '{0}_dissolved.shp'.format(i)) – BERA Nov 22 at 10:54

Use double blackslash (\) or slash(/) to separate directories in the path. Your loop variable "i" is a layer object, not the path to the layer, to get the path to the layer use:

for layer in QgsProject.instance().mapLayers().values():
    layer_path = layer.dataProvider().dataSourceUri().split('|')[0]
    output_path = 'C:\\Users\\imper\\Desktop\\' + layer.name() + '_dissolved' + '.shp'
                   {'FIELD': [], 'INPUT': layer_path, 'OUTPUT': output_path})
    iface.addVectorLayer(output_path, layer.name() + '_dissolved', 'ogr')
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