PyQGIS Virtual Layer – Creating Virtual Layer with PyQGIS

pyqgisvirtual-layer

Is it possible to create a Virtual Layer through a Python script? For example, I have a layer "road", and I would like to perform the SQL query

SELECT *
FROM road
WHERE type = 'Expressway'

Will this be possible? Is there any example I can refer to?

Best Answer

For QGIS 3, instead use QgsProject:

from qgis.core import QgsVectorLayer, QgsProject
vlayer = QgsVectorLayer( "?query=SELECT * FROM road WHERE type = 'Expressway'", "vlayer", "virtual" )
QgsProject.instance().addMapLayer(vlayer)

Related Solutions

PyQGIS Vector Layer – Creating New Empty Vector Layer with PyQGIS

This does not work any longer in qgis3. See a slightly modified answer below.

Have a look at the Memory provider as described in PyQGIS Cookbook.

Memory provider is intended to be used mainly by plugin or 3rd party app developers. It does not store data on disk, allowing developers to use it as a fast backend for some temporary layers.

# To avoid 'QVariant' is not defined error
from PyQt4.QtCore import *
# create layer
vl = QgsVectorLayer("Point", "temporary_points", "memory")
pr = vl.dataProvider()
# Enter editing mode
vl.startEditing()
# add fields
pr.addAttributes( [ QgsField("name", QVariant.String),
               QgsField("age",  QVariant.Int),
               QgsField("size", QVariant.Double) ] )
# add a feature
fet = QgsFeature()
fet.setGeometry( QgsGeometry.fromPoint(QgsPoint(10,10)) )
fet.setAttributeMap( { 0 : QVariant("Johny"),
                  1 : QVariant(20),
                  2 : QVariant(0.3) } )
pr.addFeatures( [ fet ] )
# Commit changes
vl.commitChanges()

Best Answer

Related Solutions

PyQGIS Vector Layer – Creating New Empty Vector Layer with PyQGIS

Related Question