Creating Virtual Layer with PyQGIS

Question

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?

score 22 · Answer 1 · edited Nov 04 '23 at 20:20

22

For QGIS 3, instead use QgsProject:

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

edited Nov 04 '23 at 20:20

Taras

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answered Mar 20 '19 at 17:07

rwalk

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Given current LTR QGIS version is 3.10, this answer should be the new validated one ! – sigeal Jul 04 '20 at 10:04

score 12 · Accepted Answer · edited Nov 04 '23 at 20:23

12

For QGIS 2 you could use something like the following:

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

You can find examples on how to use virtual layers through Python from the author's GitHub:

https://github.com/mhugo/qgis_vlayers/blob/master/README.md

edited Nov 04 '23 at 20:23

Taras

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answered Feb 06 '17 at 10:49

Joseph

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1

I got an error in the Python console: 'QgsMapLayerRegistry' is not defined. The SQL statement works when running in the 'Create a virtual layer' dialog. – eclipsed_by_the_moon Feb 06 '17 at 17:38
1

Did you include the 'from qgis.core import ...' line? What version are you using? – ndawson Feb 06 '17 at 19:40
@eclipsed_by_the_moon - Yes, you're correct. Edited the post to include the necessary imports (thanks to annoymous user for edit). – Joseph Feb 07 '17 at 09:56
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@Joseph Thanks for the link provided in your answer! – mgri Feb 07 '17 at 09:59
@CyT - Most welcome! Glad it worked =) – Joseph Feb 10 '17 at 09:56

Creating Virtual Layer with PyQGIS

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