Add a field which is holding the area of each record (the workflow)

mtl_buildings_workflow.py

@@ -4,10 +4,11 @@ Buildings Geometries.
 Developed by Alireza Adli
 """
 
-
-from qgis.core import QgsApplication, QgsVectorLayer, QgsProject, \
-  QgsProcessingFeedback
+from qgis.core import QgsApplication, QgsField, QgsProject, \
+  QgsProcessingFeedback, QgsVectorLayer, QgsVectorDataProvider, \
+  QgsExpressionContext, QgsExpressionContextUtils
 from qgis.analysis import QgsNativeAlgorithms
+from qgis.PyQt.QtCore import QVariant
 import processing
 import os
 from services_scripts.basic_functions import create_folders, \
@@ -17,7 +18,7 @@ from services_scripts.basic_functions import create_folders, \
 # This function loads a layer.
 # It's used to count the data records
 def load_layer(path, layer_name):
-  the_layer = QgsVectorLayer(path, layer_name, "ogr")
+  the_layer = QgsVectorLayer(path, layer_name, 'ogr')
   if not the_layer.isValid():
     print(f'{layer_name} failed to load!')
   else:
@@ -74,7 +75,7 @@ params_clipping_nrcan = {'INPUT': fixed_nrcan_layer,
                          'FILTER_EXPRESSION': '',
                          'FILTER_EXTENT': None,
                          'OUTPUT': clipped_nrcan_layer}
-processing.run("native:clip", params_clipping_nrcan)
+processing.run('native:clip', params_clipping_nrcan)
 print(f'Clipping of {fixed_nrcan_name} is completed.')
 
 # After each step, data records are counted
@@ -90,7 +91,7 @@ print(f'{clipped_nrcan_name} data count: {clipped_nrcan_length}')
 # (smoothly and efficiently)
 params_create_index_nrcan = {'INPUT': clipped_nrcan_layer,
                              'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", params_create_index_nrcan)
+processing.run('native:createspatialindex', params_create_index_nrcan)
 print(f'Creating spatial index for {clipped_nrcan_name} is completed.')
 
 # Reading Shared platform of geospatial data
@@ -102,7 +103,7 @@ geoindex, geoindex_name = load_layer(geoindex_layer, 'GeoIndex')
 print(f'{geoindex_name} data count: {geoindex.featureCount()}')
 
 params_create_index_geo = {'INPUT': geoindex_layer, 'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", params_create_index_geo)
+processing.run('native:createspatialindex', params_create_index_geo)
 
 # Fixing the GeoIndex layer geometries
 print(f'Fixing {geoindex_name} geometries')
@@ -112,11 +113,11 @@ fixed_geoindex = 'C:/Users/a_adli/PycharmProjects/' \
 params_fixing_geoindex = {'INPUT': geoindex,
                           'METHOD': 0,
                           'OUTPUT': fixed_geoindex}
-processing.run("native:fixgeometries", params_fixing_geoindex)
+processing.run('native:fixgeometries', params_fixing_geoindex)
 
 params_create_index_fixed_geo = {'INPUT': fixed_geoindex,
                                  'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", params_create_index_fixed_geo)
+processing.run('native:createspatialindex', params_create_index_fixed_geo)
 
 fixed_geoindex_read, fixed_geoindex_name = \
   load_layer(fixed_geoindex, 'Fixed NRCan')
@@ -134,7 +135,7 @@ params = {'INPUT': fixed_geoindex,
           'FILTER_EXPRESSION': '',
           'FILTER_EXTENT': None,
           'OUTPUT': clipped_geoindex_layer}
-processing.run("native:clip", params)
+processing.run('native:clip', params)
 print(f'Clipping {fixed_geoindex_name} is completed.')
 
 clipped_geoindex, clipped_geoindex_name = \
@@ -144,7 +145,7 @@ print(f'{clipped_geoindex_name} data count: {clipped_geoindex.featureCount()}')
 # Creating spatial index fo the GeoIndex layer
 params_create_index_clipped_geo = {'INPUT': clipped_geoindex_layer,
                                    'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", params_create_index_clipped_geo)
+processing.run('native:createspatialindex', params_create_index_clipped_geo)
 print(f'Creating spatial index for {clipped_geoindex_name} is completed.')
 
 # Reading the Property Assessment (AKA uniteevaluationfonciere) dataset
@@ -161,7 +162,7 @@ print(f'{property_assessment_layer_name} '
 # Creating spatial index for the GeoIndex layer
 params_create_index_property_assessment = {'INPUT': property_assessment_layer,
                                            'OUTPUT': 'Output'}
-processing.run("native:createspatialindex",
+processing.run('native:createspatialindex',
                params_create_index_property_assessment)
 print(f'Creating spatial index for '
       f'{property_assessment_layer_name} is completed.')
@@ -194,12 +195,12 @@ for each in range(num_layers):
                                     f'{(each + 1) * splitting_intervals}\r\n',
                       'OUTPUT': output_layer_path}
 
-  processing.run("native:extractbyexpression", splitting_params)
+  processing.run('native:extractbyexpression', splitting_params)
 
 # Creating spatial index for each new layer
   params_create_index_layers = {'INPUT': output_layer_path,
                                 'OUTPUT': 'Output'}
-  processing.run("native:createspatialindex", params_create_index_layers)
+  processing.run('native:createspatialindex', params_create_index_layers)
 
 # Putting the remaining features in one last layer
 # (So, overall we're going to have [num_layers + 1] layers).
@@ -217,12 +218,12 @@ last_splitting_params = {'INPUT': clipped_nrcan_layer,
                          f'$id >= {num_layers * splitting_intervals}\r\n',
                          'OUTPUT': output_layer_path}
 
-processing.run("native:extractbyexpression", last_splitting_params)
+processing.run('native:extractbyexpression', last_splitting_params)
 
 # Create spatial index for the last partition (layer)
 params_create_index_last = {'INPUT': output_layer_path,
                             'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", params_create_index_last)
+processing.run('native:createspatialindex', params_create_index_last)
 
 # Now we clip the property assessment with each of the partitions (layers)
 # from the last process. The process outputs the pairwise clipped version of
@@ -253,14 +254,14 @@ for each in range(num_clipped_layers):
                               'FILTER_EXPRESSION': '',
                               'FILTER_EXTENT': None,
                               'OUTPUT': clipped_layer}
-  processing.run("native:clip", pairwise_clipping_params)
+  processing.run('native:clip', pairwise_clipping_params)
 
   # Creating spatial index for each new layer
   params_create_index_clips = {'INPUT': clipped_layer,
                                'OUTPUT': 'Output'}
-  processing.run("native:createspatialindex", params_create_index_clips)
+  processing.run('native:createspatialindex', params_create_index_clips)
 
-print("Pairwise Clipping is completed.")
+print('Pairwise Clipping is completed.')
 
 # Finally, we merge all the clipped layers to make the
 # pairwise clipped Property Assessment layer
@@ -277,12 +278,12 @@ merging_params = {'LAYERS': pairwise_clipped_layers_path,
                   'CRS': None,
                   'OUTPUT': pairwise_clipped_property_assessment_layer}
 
-processing.run("native:mergevectorlayers", merging_params)
+processing.run('native:mergevectorlayers', merging_params)
 
 # Create spatial index for the pairwise clipped Property Assessment
 params_create_index_pairwised = \
   {'INPUT': pairwise_clipped_property_assessment_layer, 'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", params_create_index_pairwised)
+processing.run('native:createspatialindex', params_create_index_pairwised)
 
 pairwise_clipped_property_assessment, \
  pairwise_clipped_property_assessment_name = \
@@ -319,7 +320,7 @@ processing.run('native:joinattributesbylocation',
 params_create_index_joined_nrcan = \
   {'INPUT': property_assessment_nrcan_layer,
    'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", params_create_index_joined_nrcan)
+processing.run('native:createspatialindex', params_create_index_joined_nrcan)
 
 property_assessment_nrcan, property_assessment_nrcan_name = \
   load_layer(property_assessment_nrcan_layer,
@@ -350,7 +351,7 @@ processing.run('native:joinattributesbylocation',
 create_index_params = \
   {'INPUT': property_assessment_nrcan_geo_layer,
    'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", create_index_params)
+processing.run('native:createspatialindex', create_index_params)
 
 property_assessment_nrcan_geo, property_assessment_nrcan_geo_name = \
   load_layer(property_assessment_nrcan_geo_layer,
@@ -374,11 +375,11 @@ property_nrcan_geo_deleted_duplicates_layer = \
   'output_data/deleted_duplicates_property_and_all/delete_duplicates.shp'
 delete_duplicates_params = {'INPUT': property_assessment_nrcan_geo_layer,
                             'OUTPUT': property_nrcan_geo_deleted_duplicates_layer}
-processing.run("native:deleteduplicategeometries", delete_duplicates_params)
+processing.run('native:deleteduplicategeometries', delete_duplicates_params)
 
 create_index_params = {'INPUT': property_nrcan_geo_deleted_duplicates_layer,
                        'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", create_index_params)
+processing.run('native:createspatialindex', create_index_params)
 
 property_nrcan_geo_deleted_duplicates, \
  property_nrcan_geo_deleted_duplicates_name = \
@@ -392,17 +393,44 @@ singled_parts_layer = \
   'hydroquebec_archetype_gispy/data/' \
   'output_data/singled_parts/singled_parts.shp'
 
+# Multipart to single parts process: enables clicking for even small geometries
+# that used to be, mistakenly, only clickable with a bigger geometry together
+
 singled_parts_params = {'INPUT': property_nrcan_geo_deleted_duplicates_layer,
                         'OUTPUT': singled_parts_layer}
-processing.run("native:multiparttosingleparts", params)
+processing.run('native:multiparttosingleparts', params)
 
 create_index_params = {'INPUT': singled_parts_layer,
                        'OUTPUT': 'Output'}
-processing.run("native:createspatialindex", create_index_params)
+processing.run('native:createspatialindex', create_index_params)
 
 singled_parts, singled_parts_layer_name = \
  load_layer(singled_parts_layer,
             'Property Assessment Layer Joined with NRCan')
 print(f'{singled_parts_layer_name} data count: {singled_parts.featureCount()}')
 
+# Add an 'Area' field to the layer, to hold the area of each record
+
+functionalities = singled_parts.dataProvider().capabilities()
+
+if functionalities & QgsVectorDataProvider.AddAttributes:
+    new_field = QgsField('Area', QVariant.Double)
+    singled_parts.dataProvider().addAttributes([new_field])
+    singled_parts.updateFields()
+
+# Retrieve the area of each record and put it in the new added field: 'Area'
+singled_parts.startEditing()
+idx = singled_parts.fields().indexFromName('Area')
+
+
+context = QgsExpressionContext()
+context.appendScopes(QgsExpressionContextUtils.globalProjectLayerScopes(singled_parts))
+
+for feature in singled_parts.getFeatures():
+    area = feature.geometry().area()
+    feature[idx] = area
+    singled_parts.updateFeature(feature)
+
+singled_parts.commitChanges()
+
 qgs.exitQgis()

services_scripts/add_new_field.py

@@ -9,6 +9,6 @@ layer = QgsVectorLayer(
 functionalities = layer.dataProvider().capabilities()
 
 if functionalities & QgsVectorDataProvider.AddAttributes:
-    new_field = QgsField("Area", QVariant.Double)
+    new_field = QgsField('Area', QVariant.Double)
     layer.dataProvider().addAttributes([new_field])
     layer.updateFields()