Count features in layers and categories

Question

I want to automatically count features in my opened layers, and add the result in the layer name, with pyqgis. I can do it with this code :

layers = QgsProject.instance().mapLayers().values()
for layer in layers:
   fc = layer.featureCount()
   fc = str(fc)
   layer.setName(layer.name()+" ["+fc+"]")

However, it does count features in each layer, but not in each renderer category when a layer have a categorized style. I was trying something like this just to print the result :

for layer in layers:
    renderer = layer.renderer()
    renderert = renderer.type()
    if renderert == "categorizedSymbol":
        for cat in renderer.categories():
            print(cat.label+cat.featureCount())

But i get an "AttributeError: 'QgsRendererCategory' object has no attribute 'featureCount'"

Do you know how to apply the featureCount() function to layers and categories?

Answer 1

From this answer, is this code below a nicer solution ?

I just use the builtin layer function Show feature count :

layers = QgsProject.instance().mapLayers().values()
root = QgsProject.instance().layerTreeRoot()
for layer in layers:
    if layer.type() == QgsMapLayer.VectorLayer:
        myLayerNode = root.findLayer(layer.id())
        myLayerNode.setCustomProperty("showFeatureCount", True)

Answer 2

You can use collections.Counter.

from collections import Counter
layer = iface.activeLayer() # My layer 
field_categorized = 'category' # My categorized field 
c = Counter([feature[field_categorized] for feature in layer.getFeatures()]) # Loop on features of the layer 

# Result 
print(c)
Counter({0: 67, 1: 34})