PyQGIS Error using standalone script when loading a vector layer

Question

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)

• Germán Carrillo: 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.
• brgionta: 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?
• Germán Carrillo: First guess, try with C:\\OSGeo4W\\apps\\qgis\\ as prefix path.
• brgionta: Tried to no avail. Still get fatal pop-up window on that line
• Joseph: @brgionta - Try adding QgsApplication( [], False, "C:\\Users\\You\\AppData\\Local\\Temp" ) before QgsApplication.setPrefixPath("C:\\OSGeo4W\\apps\\qgis", True).

Answer 1

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)