Merging layers with same name in PyQGIS

Question

Is there a way to merge all the layers with same name using python script in QGIS in the following list;

names = [layer.name() for layer in QgsMapLayerRegistry.instance().mapLayers().values()]
print names

Output:

[u'Pois', u'Pois', u'Pois', u'Pois', u'Pois', u'Pois', u'Pois', u'Pois', u'Pois']

So that when I list my current mapLayers, all I get is one layer with all the other layers merged into it.

Answer 1

You can use processing algorithms :

import processing
processing.alghelp("qgis:mergevectorlayers")

pois_lyr_list = []
lyr_list = QgsMapLayerRegistry.instance().mapLayers()
for layer in lyr_list:
    if layer.name() == u'Pois':
         pois_lyr_list.append(layer)

processing.runandload("qgis:mergevectorlayers", pois_lyr_list, "memory:merged")

Answer 2

Here is an updated version for QGIS3. Note that I hardcoded CRS and result directory.

To get help for other CRS options you can run in Python Console:

import processing
processing.algorithmHelp('native:mergevectorlayers')

Merge layers with same name script:

import processing

grouped_layers_by_name = {}
distinct_layer_names = set()

project_layers = QgsProject.instance().layerTreeRoot().children()

for layer_item in project_layers:
    layer_name = layer_item.name()
    distinct_layer_names.add(layer_name)
    grouped_layers_by_name[layer_name] = QgsProject.instance().mapLayersByName(layer_name);

print('Total number of distinct layers: ' + str(len(distinct_layer_names)))

for layer_name in distinct_layer_names:
    print('Processing layer: ' + layer_name + '... ', end='')
    merged_layer_file_name = 'D:/merged/' + layer_name + '.gpkg'
    alg_params = {
        'LAYERS': grouped_layers_by_name[layer_name],
        'CRS': 'EPSG:3765',
        'OUTPUT': merged_layer_file_name
    }

    result = processing.run('native:mergevectorlayers', alg_params)
    print('done.')

print('All layers have been merged.')

Answer 3

Simple version updated for QGIS3

import processing

listLayers = QgsProject.instance().mapLayersByName('Points')

processing.runAndLoadResults("native:mergevectorlayers", 
                             {'LAYERS':listLayers,
                             'CRS':3006,
                             'OUTPUT':'TEMPORARY_OUTPUT'})