Use temporary vector layer in scripts

Question

I would like to create a vector layer, add a point to it and then use it in qgis algorithms.

This is what I wrote :

#create temporary layer containing center point
 point=QgsFeature()
 point.setGeometry(QgsGeometry.fromPoint(QgsPoint(center[0],center[1])))
 pointlayer=QgsVectorLayer("Point?crs=epsg:2154", "temporary_points", "memory")
 pointlayer.startEditing()
 pointlayer.addFeatures([point])
 pointlayer.commitChanges()
 #intersection between point layer and polygon layers to get names codes
 fieldname_vector=processing.runalg('qgis:intersection', parcel, pointlayer, False, None)

But when the algorithm runs, it returns

 Unable to execute algorithm
Wrong parameter value: Point?crs=epsg:2154

Is there a way to use my layer without saving it, knowing that I'll erase it in the future ?

• Clement: Ok thanks, do you know why it's impossible to use it without adding it to the layer's panel ?
• Joseph: Ignore my previous comment, you can load it in the Layers Panel without it being shown. A related question regarding this was asked before: Using in-memory vector layer with QGIS processing / SEXTANTE.

Answer 1

You need to add the memory layer to the QgsMapLayerRegistry before you can use it in processing. But you can add it without it being shown in the Layers Panel by using:

QgsMapLayerRegistry.instance().addMapLayer(pointlayer, False)

When finished, you can then do some cleanup by removing and deleting it:

QgsMapLayerRegistry.instance().removeMapLayer(pointlayer)
del pointlayer

• Orienteerix: In QGIS 3 the QgsMapLayerRegistry has been removed but the layer can be added via QgsProject.instance().addMapLayer(pointlayer, False).
• Joseph: @Orienteerix - Thanks for the extra info :)