Setting layer transparency with PyQGIS

Question

Is there a PyQGIS code to edit the transparency of rule based symbols?

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• wanderzen: You can change the opacity levels of your symbols with .setOpacity() docs.qgis.org/3.22/en/docs/pyqgis_developer_cookbook/…

Answer 1

As described in the @wanderzen's comment to this question you can use setOpacity() to change the transparency of a symbol.

Symbols themselves can be accessed from each of the rules (QgsRuleBasedRenderer::Rule) stored by the QgsRuleBasedRenderer as children of the invisible root rule.

An example to set all all rules to 75% opacity would be:

layer = iface.activeLayer()
root_rule = layer.renderer().rootRule()
for rule in root_rule.children():
 rule.symbol().setOpacity(0.75)
 
layer.triggerRepaint()

• zakros: I don't manage to make your code work. I get this error: 'QgsSingleSymbolRenderer' object has no attribute 'rootRule'
• CodeBard: @zakros This question is about changing opacity of the individual symbols of a rule based renderer. If you are using a single symbol renderer you can just use layer.setOpacity(0.75)
• zakros: Thanks for answering me. Yes but if I use setOpacity I can't change the opacity of only the selectedFeatures
• zakros: I tried this: vlayer = iface.activeLayer() vlayer.selectByExpression('"field_A"= \'category_FZ15\'', QgsVectorLayer.SetToSelection) vlayer.selectedFeatures()[0].setOpacity(1) ` But I get this: AttributeError: 'QgsFeature' object has no attribute 'setOpacity'