mtl_gis_oo/scrub_layer_class.py

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from qgis.core import QgsApplication, QgsField, QgsProject, \
QgsProcessingFeedback, QgsVectorLayer, QgsVectorDataProvider, \
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QgsExpressionContext, QgsExpressionContextUtils, edit
from qgis.PyQt.QtCore import QVariant
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from qgis.analysis import QgsNativeAlgorithms
from basic_functions import *
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import processing
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class ScrubLayer:
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def __init__(self, qgis_path, layer_path, layer_name):
# Set the path to QGIS installation
QgsApplication.setPrefixPath(qgis_path, True)
# Initialize QGIS application
qgs = QgsApplication([], False)
qgs.initQgis()
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self.layer_path = layer_path
self.layer_name = layer_name
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self.layer = self.load_layer()
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self.data_count = self.layer.featureCount()
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def load_layer(self):
the_layer = QgsVectorLayer(self.layer_path, self.layer_name, 'ogr')
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if not the_layer.isValid():
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raise ValueError(f'Failed to load layer {self.layer_name} from {self.layer_path}')
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else:
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QgsProject.instance().addMapLayer(the_layer)
return the_layer
def fix_geometries(self, fixed_layer):
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())
fix_geometries_params = {
'INPUT': self.layer,
'METHOD': 0,
'OUTPUT': fixed_layer
}
processing.run("native:fixgeometries", fix_geometries_params)
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def create_spatial_index(self):
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())
create_spatial_index_params = {
'INPUT': self.layer,
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'OUTPUT': 'Output'
}
processing.run("native:createspatialindex", create_spatial_index_params)
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print(f'Creating Spatial index for {self.layer_name} is completed.')
def spatial_join(self, joining_layer_path, joined_layer_path):
"""In QGIS, it is called 'Join attributes by Location'"""
params = {'INPUT': self.layer,
'PREDICATE': [0],
'JOIN': joining_layer_path,
'JOIN_FIELDS': [],
'METHOD': 0,
'DISCARD_NONMATCHING': False,
'PREFIX': '',
'OUTPUT': joined_layer_path}
feedback = QgsProcessingFeedback()
processing.run('native:joinattributesbylocation', params, feedback=feedback)
print(f'Spatial Join with input layer {self.layer_name} is completed.')
def clip_layer(self, overlay_layer, clipped_layer):
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"""This must be tested"""
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())
clip_layer_params = {
'INPUT': self.layer_path,
'OVERLAY': overlay_layer,
'FILTER_EXPRESSION': '',
'FILTER_EXTENT': None,
'OUTPUT': clipped_layer
}
processing.run("native:clip", clip_layer_params)
print(f'Clipping of {self.layer_name} is completed.')
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def multipart_to_singleparts(self, singleparts_layer_path):
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())
params = {'INPUT': self.layer,
'OUTPUT': singleparts_layer_path}
processing.run("native:multiparttosingleparts", params)
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def split_layer(self):
pass
def delete_duplicates(self, deleted_duplicates_layer):
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())
params = {'INPUT': self.layer_path,
'OUTPUT': deleted_duplicates_layer}
processing.run("native:deleteduplicategeometries", params)
def delete_field(self, field_name):
QgsApplication.processingRegistry().addProvider(QgsNativeAlgorithms())
with edit(self.layer):
# Get the index of the column to delete
idx = self.layer.fields().indexFromName(field_name)
# Delete the field
self.layer.deleteAttribute(idx)
# Update layer fields
self.layer.updateFields()
def add_field(self, new_field_name):
functionalities = self.layer.dataProvider().capabilities()
if functionalities & QgsVectorDataProvider.AddAttributes:
new_field = QgsField(new_field_name, QVariant.Double)
self.layer.dataProvider().addAttributes([new_field])
self.layer.updateFields()
def assign_area(self, field_name):
self.layer.startEditing()
idx = self.layer.fields().indexFromName(field_name)
context = QgsExpressionContext()
context.appendScopes(QgsExpressionContextUtils.globalProjectLayerScopes(self.layer))
for feature in self.layer.getFeatures():
area = feature.geometry().area()
feature[idx] = area
self.layer.updateFeature(feature)
self.layer.commitChanges()
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def __str__(self):
return f'The {self.layer_name} has {self.data_count} records.'
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@staticmethod
def cleanup():
QgsApplication.exitQgis()
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