Improving select and edit features performance of QGIS plugin?

Question

I wrote a plugin for selecting and instant updating the value of the selected feature in the attribute table. I tested with a big shapefile and to select and edit 5 features takes ~5 seconds. Which isn't really fast.

Can someone look at the piece of code and give me suggestions for how I can do for faster editing?

        lRect = self.canvas.mapRenderer().mapToLayerCoordinates(layer, r)
        layer.select(lRect, False)
        layer.startEditing()
        #for feat in layer.selectedFeatures():
        for feat in layer.selectedFeaturesIterator():
            feat["foo"] = my_value
            layer.updateFeature(feat)
        layer.commitChanges()
        layer.removeSelection()

I could use selectedFeatures() or selectedFeaturesIterator() but I tested it with both and I got nearly the same result (time).

Answer 1

I think this code with a QgsFeatureRequest() object speed up a bit:

        request = QgsFeatureRequest()
        lRect = self.canvas.mapRenderer().mapToLayerCoordinates(layer, r)
        request.setFilterRect(lRect)
        layer.startEditing()
        for feat in layer.getFeatures(request):
            feat['foo'] = value
            layer.updateFeature(feat)
        layer.commitChanges()
        layer.removeSelection()

found here http://docs.qgis.org/testing/en/docs/pyqgis_developer_cookbook/vector.html#iterating-over-a-subset-of-features