How to classify the symbology with changed values in a field after using loadNamedStyle in PYQGIS?

Question

First of all, I have exported a layer style from a layer as a QML file including draw effects (symbology --> layer rendering --> draw effects) in symbology. Note that, I have checked all the categories while saving it (see below image).

Then, I have changed the values in the field which I have configured a Graduated Symbology with. Then I tried to load the QML file with loadNamedStyle(). It did not change the legend and classes automatically. Therefore, I have tried a few things to automatically update that.

field = 'SPREAD'
stylepath = '/path_to_my_layer_style.qml'
layer = iface.activeLayer()
layer.loadNamedStyle(stylePath)
renderer = layer.renderer()
sym = renderer.sourceSymbol()
grad = renderer.sourceColorRamp()
renderVal = renderer.createRenderer(layer,field,5,0,sym,grad)
layer.setRenderer(renderer)

It worked. However, the effects in that QML file has disappeared after that. I also do not think this is the best way to do that. Is there a more convenient way to classify the symbology with new values after loading QML file in PYQGIS?

Answer 1

Ok, I found a solution. Here is how I did,

layer.loadNamedStyle(stylePath)
renderer = layer.renderer()

renderer.updateClasses(layer,0,5) # Update the QgsGraduatedSymbologyRenderer.mode and set the classes up to 5
renderer.updateRangeLabels() # Update label range
renderer.updateColorRamp() # Update the color ramp
iface.layerTreeView().refreshLayerSymbology(layer.id()) # Refresh legend on the interface
layer.reload() 

With this way, symbology is being triggered to classify again for the determined parameters and also the symbol effects does not disappear.