qgis3_standalone_osx.py

"""
Standalone python script for QGIS3 on OSX.
"""
import os
import sys

# Define plugin locations from QGIS3
sys.path.append('/Applications/QGIS3.app/Contents/Resources/python/')
sys.path.append('/Applications/QGIS3.app/Contents/Resources/python/plugins')
# Define Qt5 plugin path since Qt5 can't find it
# http://osgeo-org.1560.x6.nabble.com/QGIS-3-Standalone-Python-Script-tp5373335p5373573.html
os.environ['QT_QPA_PLATFORM_PLUGIN_PATH'] = '/Applications/QGIS3.app/Contents/PlugIns'

# With path set, import QGIS3
from qgis.core import QgsApplication, QgsProcessingFeedback, QgsVectorLayer

# Initialize the app or QGIS3 will crash
QgsApplication.setPrefixPath("/Applications/QGIS3.app/Contents/MacOS", True)
app = QgsApplication([], False)
app.initQgis()

# Check if vector layer is valid to make sure everything is working
roads = sys.argv[1]
water = sys.argv[2]
vroads = QgsVectorLayer(roads, 'vroads', 'ogr')
vwater = QgsVectorLayer(water, 'vwater', 'ogr')
if not vroads.isValid():
    print("Roads layer invalid.")
else:
    print("Roads layer valid.")

if not vwater.isValid():
    print("Water layer invalid.")
else:
    print("Water layer valid.")

# Initialize processing and add native tools
from qgis.analysis import QgsNativeAlgorithms
import processing  # processing causes psycopg2-binary warning
from processing.core.Processing import Processing
Processing.initialize()
app.processingRegistry().addProvider(QgsNativeAlgorithms())

# Set parameters for QGIS3 Line Intersection tool
params = { 
    'INPUT':roads,
    'INTERSECT':water,
    'INPUT_FIELDS':'ID',
    'INTERSECT_FIELDS':'GFID',
    'OUTPUT':sys.argv[3],
}

feedback = QgsProcessingFeedback()
print("Starting intersections test...")
results = processing.run("native:lineintersections", params, feedback=feedback)
print(results)
app.exitQgis()