Is there a way to hide range categories using Python code on a vector layer?

Question

I have a routine to create a layer with 6 categories (see 1st graph) based on the values of the attributes. Is there a way I can hide the categories (see the 2nd graph) using Python code?

def mapRange(layerName, fieldName):

    #https://gis.stackexchange.com/questions/31789/setting-color-of-feature-depending-on-attributes-with-pyqgis
    layerCat = QgsProject.instance().mapLayersByName(layerName)[0]

    values = (
    ('0.0-0.2', 0.0, 0.2, 'red'),
    ('0.2-0.4', 0.2, 0.4, 'orange'),
    ('0.4-0.6', 0.4, 0.6, 'yellow'),
    ('0.6-0.8', 0.6, 0.8, 'green'),
    ('0.8-1.0', 0.8, 1.0, 'blue'),
    ('Dry', -9999, -0.001, 'gray'))

    # create a category for each item in values
    ranges = []
    for label, lower, upper, color in values:
        symbol = QgsSymbol.defaultSymbol(layerCat.geometryType())
        symbol.setColor(QColor(color))
        #https://gis.stackexchange.com/questions/200094/how-to-define-border-colour-for-rule-based-style-using-pyqgis/220662
        layer_style = {}
        layer_style['color'] = color
        layer_style['color_border'] = color
        symbol_layer = QgsSimpleFillSymbolLayer.create(layer_style)
        if symbol_layer is not None:
            symbol.changeSymbolLayer(0, symbol_layer)

        rng = QgsRendererRange(lower, upper, symbol, label)
        ranges.append(rng)

    #create the renderer and assign it to a layer
    renderer = QgsGraduatedSymbolRenderer(fieldName, ranges)
    layerCat.setRenderer(renderer)

So you want to programmatically collapse the legend in the table of contents? — alphabetasoup, Jul 18 '19 at 00:10
Yes. I have many of these layers created in each simulation run, and just want to open the legend of the layer of interest. — RRCH, Jul 18 '19 at 03:11

Ben W · Answer 1 · 2019-07-18T04:58:40.593

Here is a minimal example of how to access layer tree objects such as QgsLayerTreeLayer or QgsLayerTreeGroup. These inherit the method setExpanded() from the QgsLayerTreeNode base class. So you can do the following:

layer_name = 'Name_of_your_layer'
p = QgsProject().instance()
r = p.layerTreeRoot()
c = r.children()
ll = [l for l in c if l.name() == layer_name][0]
ll.setExpanded(False) #Pass boolean value (True or False) to expand or collapse legend nodes

You can also use the isExpanded() method to check if layer tree items are already expanded or not. In this way, you could collapse all items like:

for l in c:
    if l.isExpanded():
        l.setExpanded(False)

And expand all:

for l in c:
    if not l.isExpanded():
        l.setExpanded(True)

score 1 · Answer 2 · answered Jul 18 '19 at 15:48

Thanks, Ben. Your answer really helps. I modified your code a little because the layers of interest are under a group.

from qgis.core import QgsLayerTreeLayer, QgsLayerTreeGroup
group_name = "simResultsGroup"
layer_name = "simResults"
p = QgsProject().instance()
r = p.layerTreeRoot()
c = r.children()

for l in c:
    if l.name() == group_name:
        for aLayer in l.findLayers():
            if aLayer.isExpanded():
                aLayer.setExpanded(False)

Is there a way to hide range categories using Python code on a vector layer?

2 Answers2

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