Clipping in PyQGIS2 working but error in PyQGIS3 (argument 1 has unexpected type 'str')

Question

I am trying to clip streets by a layer with municipalities in them. I was trying to run this script in QGIS3 but obtain the error hereunder.

Traceback (most recent call last): File "C:\OSGEO4~1\apps\Python37\lib\code.py", line 90, in runcode exec(code, self.locals) File "", line 1, in File "", line 11, in File "C:/OSGEO4~1/apps/qgis/./python/plugins\processing\tools\general.py", line 105, in run return Processing.runAlgorithm(algOrName, parameters, onFinish, feedback, context) File "C:/OSGEO4~1/apps/qgis/./python/plugins\processing\core\Processing.py", line 130, in runAlgorithm context = dataobjects.createContext(feedback) File "C:/OSGEO4~1/apps/qgis/./python/plugins\processing\tools\dataobjects.py", line 72, in createContext context.setFeedback(feedback) TypeError: QgsProcessingContext.setFeedback(): argument 1 has unexpected type 'str'

I tried to run the script in QGIS2 and it works perfectly (changing run to runalg off course).

I checked the documentation of clipping in PyQGIS3 but I can't figure out what I am doing wrong. I hope someone has some insights for me.

import processing

streets = QgsVectorLayer(r"C:\Users\Me\Desktop\Test\\streets_fix.shp", "streets", "ogr")
if not streets.isValid():
  print("Layer failed to load!")

municipalities= QgsVectorLayer(r"C:\Users\Me\Desktop\Test\municipalities.shp", "municipalities", "ogr")
if not municipalities.isValid():
  print("Layer failed to load!")

processing.run("qgis:clip", municipalities, streets, r"C:\Users\Me\Desktop\Test\clipttest1.shp")

Answer 1

The way how the parameters will be passed has changed in QGIS3, see https://docs.qgis.org/testing/en/docs/user_manual/processing/console.html

in your case it should be:

processing.run("qgis:clip", {'INPUT': streets,'OVERLAY': municipalities, 'OUTPUT': 'C:/Users/Me/Desktop/Test/clipttest1.shp'})