Creating geometry less memory layer using PyQGIS

Question

I'm writing a QGIS plugin and I need to create a table with some attributes that, in a second moment, I'll load in a SpatiaLite database.

The table is created as a memory layer, but as I said, it is just an attribute table, so the features don't have any geometric requirements.

I'm not able to create a memory layer without geometry. Is there a way to do that?

From the cookbook it seems it is not possible to create a geometryless memory layer.

I thought it was possible to set the geometry after the layer creation using a combination of QgsGeometry and from Wkb with a specific option activated.

But I have not been able to do that.

Does someone have some suggestions?

Answer 1

Since QGIS 2.14 there is a simple way to do that. See the QGIS API documentation for more details.

Just write None as the path= parameter of the QgsVectorLayer:

from qgis.core import QgsVectorLayer, QgsProject

layer = QgsVectorLayer(path='None', baseName='table_name', providerLib='memory')
QgsProject.instance().addMapLayer(layer)

# In PyQGIS 2:
# QgsMapLayerRegistry.instance().addMapLayer(layer) 

Answer 2

I haven't really worked with plugins so not sure this solution would apply in your situation but I use the following code to create a geometry-less polygon memory layer:

from PyQt4.QtCore import *

# Create memory layer
layer = QgsVectorLayer("Polygon?crs=epsg:4326", "Table", "memory")
QgsMapLayerRegistry.instance().addMapLayer(layer)

# Begin editing memory layer and create 3 fields
layer.startEditing()
provider = layer.dataProvider()
provider.addAttributes([QgsField("Name", QVariant.String),QgsField("Area", QVariant.Int),QgsField("Size", QVariant.Double)])
layer.updateFields()

# Add a feature with attributes (and without geometry) to populate the 3 fields
attr = layer.dataProvider()
feat = QgsFeature()
feat.setAttributes(["UK", 151, 33.33])
attr.addFeatures([feat])

layer.commitChanges()