Find the Position of a Layer in the TOC PyQGIS3

Question

I need to find a layer in the TOC and get its position (which can vary) so that I can add a group after that layer. I can get the layer I want to reference easily enough:

root = QgsProject.instance().layerTreeRoot()
last_layer = QgsProject.instance().mapLayersByName('next_ids')[0]

What I want to do is add group after that layer:

lyr_pos = [index in TOC of last_layer]  # This is what I need to get
self.err_group = root.insertGroup(lyr_pos + 1, GROUP_NAME)

Answer 1

You need the layer index relative to its parent group, and then you use such parent group to finally insert your new group, in this way:

# Get relevant objects
root = QgsProject.instance().layerTreeRoot()
layer_node = root.findLayer(layer)  # layer is a QgsMapLayer
parent_group = layer_node.parent()

# Get layer index
idx = parent_group.children().index(layer_node)

# Now insert the new group!
parent_group.insertGroup(idx + 1, "New Group")