Adding existing QgsVectorLayer to QGIS Project

Question

I know I can pull a vector file into my current project using:

vlayer = iface.addVectorLayer(r"S:/Data/Natural_Earth_quick_start/110m_cultural/ne_110m_admin_0_countries.shp", "admin", "ogr")

But if I create my layer using something like:

vlayer = QgsVectorLayer(r"S:/Data/Natural_Earth_quick_start/110m_cultural/ne_110m_admin_0_countries.shp", "admin", "ogr")

and then I do some processing on vlayer.

How do I add it to the current project or map layers list?

Answer 1

With addMapLayer() method to add an existing single layer:

vlayer = QgsVectorLayer("some/path/to/shapefile.shp", "admin", "ogr")
QgsProject.instance().addMapLayer(vlayer)

With addMapLayers() method to add existing multiple layers:

vlayer1 = QgsVectorLayer("some/path/to/shapefile1.shp", "admin1", "ogr")
vlayer2 = QgsVectorLayer("some/path/to/shapefile2.shp", "admin2", "ogr")
layers = [vlayer1 , vlayer2]
QgsProject.instance().addMapLayers(layers)