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I've been able to execute the command below in the Python console in QGIS. I am able to execute from qgis.core import * and import qgis.utils with no errors in the OSGeo4W shell but adding the layer I am still getting QObject::connect: Cannot connect <null>::raiseError< QString > to QgsVectorLayer::raiseError< QString >

The script below works in the Python console within QGIS. My paths are set in Environment Variables as: PYTHONPATH=c:\OSGeo4W\apps\qgis\python and PATH=c:\OSGeo4W\apps\qgis\bin

from qgis.core import *
import gdal
import qgis.utils

QgsApplication.setPrefixPath("C:\\OSGeo4W\\apps\\qgis", True)
QgsApplication.initQgis()          
print QgsApplication.showSettings()

layer = QgsVectorLayer('/path/to/shapefile_folder/test.shp', 'test', 'ogr')

if not layer.isValid():
    print "Layer failed to load!"

else:
    print "Layer was loaded successfully!"

QgsMapLayerRegistry.instance().addMapLayer(layer)
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  • Have a look at docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/… You're only missing a few lines that must be always present when running Python scripts out of QGIS. Apr 1, 2016 at 21:27
  • I've edited the code above. When running the modified code, a pop-up window stating "python.exe has stopped working" shows up. I've gone line by line in the code and it seems that QgsApplication.initQgis() is crashing Python. Any thoughts?
    – brgionta
    Apr 1, 2016 at 21:43
  • 1
    First guess, try with C:\\OSGeo4W\\apps\\qgis\\ as prefix path. Apr 1, 2016 at 21:46
  • Tried to no avail. Still get fatal pop-up window on that line
    – brgionta
    Apr 1, 2016 at 21:54
  • @brgionta - Try adding QgsApplication( [], False, "C:\\Users\\You\\AppData\\Local\\Temp" ) before QgsApplication.setPrefixPath("C:\\OSGeo4W\\apps\\qgis", True).
    – Joseph
    Apr 4, 2016 at 10:04

1 Answer 1

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from qgis.core import *

import gdal
import qgis.utils

QgsApplication.setPrefixPath("C:\OSGeo4W64\apps\qgis", True)

qgs = QgsApplication([], True)

qgs.initQgis()

print QgsApplication.showSettings()

layer = QgsVectorLayer('C:\Users\path to your shape\CB.shp', 'CB', 'ogr')

if not layer.isValid():

    print "Layer failed to load!"

else:

    print "Layer was loaded successfully!"

QgsMapLayerRegistry.instance().addMapLayer(layer)

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