Returning correct layer name in PyQGIS

Question

I have seen this type of question posed a few times on this site. The solutions that I have gleamed from these questions has helped me. But I have not been able to get my script to produce a result that I would like.

I have a layer in my QGIS 3.10 map called "warn", the actual file path and name is "C:\temp\warn1.shp". I am writing a Toolbox to perform a series of processes on this "warn"-file, with the intention that this file will be called something different in the future.

Some Examples that I have used:

• Getting layer by name in PyQGIS?
• Activating layer by its name in PyQGIS
• How get layer by name in PyQGIS 3.0?

I set up the parameters for the Toolbox as described in the QGIS Template:

self.addParameter(
            QgsProcessingParameterFeatureSource(
                'INPUT',
                self.tr('Area'),
                [QgsProcessing.TypeVectorPolygon]
            )
        )
    

I call this input in the main script:

Polygon = parameters['INPUT']

When I try and confirm the name of the input using a print statement, a value is returned, but the name contains what appears to be an identifier:

print (Polygon)

Returns:

warn1_940166d7_22bc_47bf_b76c_d75462802047

When I use the Polygon variable in the definition of the layer:

layer = QgsProject.instance().mapLayersByName(Polygon)[0]

I get an "index out of range" error. Which is expected, as the name does not exist in the map.

How can I return the name of the layer, as it appears in Layer View (Table of Contents)?

In this case I would like "warn" returned.

Answer 1

I've achieved this by a little workaround :

from qgis.utils import iface  # add this in the list of imports
#
#
class My_model(QgsProcessingAlgorithm):

    def initAlgorithm(self, config=None):
        # ...

    def processAlgorithm(self, parameters, context, model_feedback):
        # ...
        lyr_list = iface.layerTreeView().layerTreeModel().rootGroup().layerOrder()
        lyr_dict = {lyr.id(): (lyr.name(), lyr) for lyr in lyr_list}
        if parameters['INPUT'] in lyr_dict:
                print(lyr_dict[parameters['INPUT']][0])
                polygon = lyr_dict[parameters['INPUT']][0]
                layer = lyr_dict[parameters['INPUT']][1]

Answer 2

@Keagan Allan answered to his own question

Using the accepted answer I added the following to my code:

lyr_list = iface.layerTreeView().layerTreeModel().rootGroup().layerOrder()
lyr_dict = {lyr.id(): lyr.name() for lyr in lyr_list}
if parameters['INPUT'] in lyr_dict:
      print(lyr_dict[parameters['INPUT']])
      polygon = lyr_dict[parameters['INPUT']]
      layer = QgsProject.instance().mapLayersByName(polygon)[0]