[GIS] Show QGIS feature count via console on existing layers

pyqgispythonqgis

I want to make a script that toggles feature count on for all vector layers. I followed the following article: Show feature count of layer via Python console / PyQGIS.

Instead of adding new layers with feature count I'd like to switch on GUI feature count on existing layers. I adapted the code in the article so that myLayer is substituted with an existing layer that I retrieved by listing the layers.

The new layer made by the unadapted code to myLayerNode:

<qgis._core.QgsLayerTreeLayer object at 0x000000001FEC4950>

The existing layer after saving it in myLayerNode:

 <qgis._core.QgsLayerTreeLayer object at 0x000000001FEC49D8>

The new layer feature count can be toggled on/off using:

myLayerNode.setCustomProperty("showFeatureCount", True)

To my knowledge this should work but it doesn't…

#Make a list of layers
qgis.utils.iface.iface = iface
layers = qgis.utils.iface.iface.legendInterface().layers()

## reference to the layer tree
root = QgsProject.instance().layerTreeRoot()

## pick one layer to change featurecount
myLayer = layers[5]
myLayerNode = QgsLayerTreeLayer(myLayer)
#root.insertChildNode(5, myLayerNode)

## set custom property
myLayerNode.setCustomProperty("showFeatureCount", True)

myLayerNode.customProperty("showFeatureCount")
## the result is True

myLayerNode.customProperties()
## the result is a list [u'showFeatureCount']

Any idears?

Best Answer

Not completely sure why your code doesn't work but the following works for me in the Python console:

To see the feature count for a specific layer:

root = QgsProject.instance().layerTreeRoot()
for child in root.children():
    if isinstance(child, QgsLayerTreeLayer):
        if child.layerName() == "LAYER_NAME":
            child.setCustomProperty("showFeatureCount", True)

To see the feature count of all layers:

root = QgsProject.instance().layerTreeRoot()
for child in root.children():
    if isinstance(child, QgsLayerTreeLayer):
        child.setCustomProperty("showFeatureCount", True)

Related Solutions

QGIS PyQGIS – Show Feature Count of Layer via Python Console

That is pretty simple by using custom properties by the setCustomProperty() method.

The below example adds a memory layer to the legend and set the "showFeatureCount" property to True (you can run it from pyqgis console):

## create the memory layer and add to the registry
myLayer = QgsVectorLayer("Point", "myLayer", "memory")
QgsMapLayerRegistry.instance().addMapLayer(myLayer, False)

## reference to the layer tree
root = QgsProject.instance().layerTreeRoot()

## adds the memory layer to the layer node at index 0
myLayerNode = QgsLayerTreeLayer(myLayer)
root.insertChildNode(0, myLayerNode)

## set custom property
myLayerNode.setCustomProperty("showFeatureCount", True)

To get a specific property of the current layer (node layer) in layer tree you can use customProperty() or customProperties() to get all the stored properties for that layer:

myLayerNode.customProperty("showFeatureCount")
## the result is True

myLayerNode.customProperties()
## the result is a list [u'showFeatureCount']

[GIS] Batch add column to layers and add layer prefix in PyQGIS

You can achieve it by running the following code snippet in the QGIS Python console:

from PyQt4.QtCore import QVariant
for layer in QgsMapLayerRegistry.instance().mapLayers().values():
    prefix = layer.name().split("_")[0]
    res = layer.dataProvider().addAttributes([QgsField("density", QVariant.String)])
    layer.updateFields()
    fieldIndex = layer.dataProvider().fieldNameIndex( "density" )
    attrFeatMap = {}
    attrMap = { fieldIndex : prefix }
    for feature in layer.getFeatures():
        attrFeatMap[ feature.id() ] = attrMap
    layer.dataProvider().changeAttributeValues( attrFeatMap )

I assume the only layers you have loaded in the QGIS ToC are those you want to modify. Otherwise, you would need to validate things like the layer type (i.e., you don't want the script to run on raster layers).

The script iterates through layers loaded into QGIS, extracts the prefix from their names, creates the text field density, builds a dictionary like this:

{ featureId : { fieldIndex : value } }

for each feature, and finally, applies the dictionary to change features' density values.

enter image description here

Let me know if something is not clear.

Best Answer

Related Solutions

QGIS PyQGIS – Show Feature Count of Layer via Python Console

[GIS] Batch add column to layers and add layer prefix in PyQGIS

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