Python editing of QGIS layer metadata

Question

I want to feed metadata (title, attribution, etc) to a lot of raster layers in a QGIS project. From what I have read, I managed fine to get hold of metadata from the QGIS python console, using simple code like:

my_layer= QgsProject.instance().mapLayersByName('layer_of_interest')[0]
my_layer_title = my_layer.metadata().title()
my_layer_rights = my_layer.metadata().rights()

I can change the name of the layer (with immediate effect) like this:

my_layer.setName("New layer name")

So, I figured could do something similar to update metadata, so I tried:

my_layer.metadat().setTitle("New title")

which threw no errors nor warnings, but it didn't change the metadata at all, at least nothing I could see from the QGIS GUI. Does anybody know how to do this, or could point me in the right direction?

Answer 1

Find the solution myself. Some more trials showed me that the solution to this is a two-step process. 1) feed de new metadata to "layers metadata" object and then do a set metadata command to the layer object, like so:

# Retrieve layer and metadata objects
my_layer= QgsProject.instance().mapLayersByName('layer_of_interest')[0]
my_layer_meta = my_layer.metadata()

# 1. Do the metadata updating as needed
my_layer_meta.setTitle("New title")
my_layer_meta.setRights(
    ["First attribution right", "Second attribution right"]
)
my_layer_meta.setParentIdentifier("a parent identifier")
my_layer_meta.setIdentifier("an identifier")
my_layer_meta.setType("a type")
my_layer_meta.setLanguage("a language")
my_layer_meta.setAbstract("an abstract")

# 2. "commit" updated metadata
my_layer.setMetadata(my_layer_meta)

Then I get the new metadata updated at QGIS GUI as can be seen in layer properties. Done!

Documentation :

• QgsAbstractMetadataBase class.