"QgsProcessingException: Could not create memory layer" error while running QGIS Processing algorithm

Question

I am trying to run processing algorithms in Python code editor inside QGIS. Here is my code:

zones = QgsVectorLayer('C:/Users/pamidiashoka/Downloads/OP_Pen/boundaries.shp', 'zone boundaries', 'ogr')

points = QgsVectorLayer('C:/Users/pamidiashoka/Downloads/OP_Pen/666_KAMARLE_Adharne/666_KAMARLE_Adharne.shp', 'zone boundaries', 'ogr')

extr = processing.runAndLoadResults('qgis:extractbyexpression', {'INPUT': points,
                    'EXPRESSION':f"filename = '2A_2_Village_Internal_Road_1'",
                    'OUTPUT': 'TEMPORARY_OUTPUT'})
        
cnt = processing.runAndLoadResults('qgis:extractbylocation', {'INPUT':zones,
                    'PREDICATE': 0,
                    'INTERSECT' : extr['OUTPUT'],
                    'OUTPUT': 'TEMPORARY_OUTPUT'})

The first algorithm is giving proper output and adding a new layer to the panel but the second one is throwing an error. Here is the error I am getting

Traceback (most recent call last):
  File "C:\PROGRA~1\QGIS32~1.0\apps\Python39\lib\code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 1, in <module>
  File "<string>", line 13, in <module>
  File "C:\PROGRA~1/QGIS32~1.0/apps/qgis/./python/plugins\processing\tools\general.py", line 151, in runAndLoadResults
    return Processing.runAlgorithm(alg, parameters=parameters, onFinish=handleAlgorithmResults, feedback=feedback,
  File "C:\PROGRA~1/QGIS32~1.0/apps/qgis/./python/plugins\processing\core\Processing.py", line 187, in runAlgorithm
    ret, results = execute(alg, parameters, context, feedback, catch_exceptions=False)
  File "C:\PROGRA~1/QGIS32~1.0/apps/qgis/./python/plugins\processing\gui\AlgorithmExecutor.py", line 72, in execute
    results, ok = alg.run(parameters, context, feedback, {}, False)
_core.QgsProcessingException: Could not create memory layer

What is the cause of this error and how can I resolve this issue?

Pierrick Rambaud · Accepted Answer · 2022-07-25 07:02:41Z

0

you should try this:

cnt = processing.runAndLoadResults('qgis:extractbylocation', {'INPUT':zones,
                    'PREDICATE': 0,
                    'INTERSECT' : extr,
                    'OUTPUT': 'TEMPORARY_OUTPUT'})

edited Jul 25, 2022 at 7:02

Pierrick Rambaud

3,4601 gold badge17 silver badges62 bronze badges

answered Jul 25, 2022 at 5:42

Satya Dalei

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It has to be extr['OUTPUT'], otherwise the following exception will arise: Could not load source layer for INTERSECT: invalid value

Taras
– Taras ♦

2025-06-25 09:07:35 +00:00
Commented Jun 25 at 9:07

Add a comment |

Taras · Accepted Answer · 2025-06-25 06:25:55Z

I could get the same error:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "Untitled-1", line 9, in <module>
  File "C:\PROGRA~1/QGIS34~1.2/apps/qgis/./python/plugins\processing\tools\general.py", line 156, in runAndLoadResults
    return Processing.runAlgorithm(
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\PROGRA~1/QGIS34~1.2/apps/qgis/./python/plugins\processing\core\Processing.py", line 214, in runAlgorithm
    ret, results = execute(
                   ^^^^^^^^
  File "C:\PROGRA~1/QGIS34~1.2/apps/qgis/./python/plugins\processing\gui\AlgorithmExecutor.py", line 74, in execute
    results, ok = alg.run(parameters, context, feedback, {}, False)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
_core.QgsProcessingException: Could not create memory layer

after executing this piece of code:

zones = QgsVectorLayer('C:/Users/pamidiashoka/Downloads/OP_Pen/boundaries.shp', 'zone boundaries', 'ogr')

params = {
    'INPUT' : zones, 
    'EXPRESSION' : f"filename = '2A_2_Village_Internal_Road_1'",
    'OUTPUT' : 'TEMPORARY_OUTPUT'
    }
    
result = processing.runAndLoadResults("qgis:extractbyexpression", params)['OUTPUT']

This is happening due to the invalid 'zone boundaries' layer, which I obviously do not have on my PC. However, in your case it could be a wrong source path. Therefore, it is suggested to check the layer's validity before applying any geoalgorithm with the .isValid() method of the QgsMapLayer class:

if zones.isValid() and points.isValid():
   ...

Also, one could improve their code with nesting the Python's try/except-block.

References:

Generating invalid Vector layer in QGIS

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