Removing a joined layer using PyQGIS?

Question

I have two layers that I want to remove using PyQGis as part of a larger script. The first layer I can removed using:

QgsMapLayerRegistry.instance().removeMapLayer( shp.id() )

However, it seems that the second layer (the Joined layer) cannot be removed in the same way as I get the following error:

QgsMapLayerRegistry.instance().removeMapLayer( result.id() )

Traceback (most recent call last):
File "<input>", line 1, in <module>
AttributeError: JoinAttributes instance has no attribute 'id'

Does anyone happen to know a way to remove the Joined layer with PyQGIS?

Answer 1

U used the toolbox algorithm "qgis:joinattributestable".

This algorithm creates a new table named Joined layer (i don't know whether the algorithm let u choose its name ...)

Result is not a reference to any QgsVectorLayer but is a JoinAttributes instance which enables you to retrieve some information about the algorithm you just launched.

So result.id generates an error since id is not an attribute of this class.

RemoveAllMapLayers looks really like an odd solution to me ... better use something like :

jl = QgsMapLayerRegistry.instance().mapLayersByName("Joined layer")[0]
QgsMapLayerRegistry.instance().removeMapLayer(jl.id())

Answer 2

After working on the problem for a little while longer I was able to find an answer, although not an ideal one.

What I ended up doing was using

QgsMapLayerRegistry.instance().removeAllMapLayers()

to remove all the map layers, and then afterwards re-adding the ones I need.

While this does get the job done, it probably isn't the most elegant or efficient solution. If anyone knows a better way please post it.