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86 lines
3.2 KiB
Python
86 lines
3.2 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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ExtractByExpression.py
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---------------------
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Date : October 2016
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Copyright : (C) 2016 by Nyall Dawson
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***************************************************************************
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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***************************************************************************
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"""
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__author__ = 'Nyall Dawson'
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__date__ = 'October 2016'
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__copyright__ = '(C) 2016, Nyall Dawson'
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# This will get replaced with a git SHA1 when you do a git archive
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__revision__ = '$Format:%H$'
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from qgis.core import (QgsExpression,
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QgsFeatureRequest,
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QgsApplication,
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QgsProcessingUtils)
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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from processing.core.parameters import ParameterVector
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from processing.core.outputs import OutputVector
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from processing.core.GeoAlgorithm import GeoAlgorithm
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from processing.core.parameters import ParameterExpression
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class ExtractByExpression(GeoAlgorithm):
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INPUT = 'INPUT'
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EXPRESSION = 'EXPRESSION'
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OUTPUT = 'OUTPUT'
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def icon(self):
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return QgsApplication.getThemeIcon("/providerQgis.svg")
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def svgIconPath(self):
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return QgsApplication.iconPath("providerQgis.svg")
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def tags(self):
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return self.tr('extract,filter,expression,field').split(',')
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def group(self):
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return self.tr('Vector selection tools')
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def name(self):
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return 'extractbyexpression'
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def displayName(self):
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return self.tr('Extract by expression')
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def defineCharacteristics(self):
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self.addParameter(ParameterVector(self.INPUT,
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self.tr('Input Layer')))
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self.addParameter(ParameterExpression(self.EXPRESSION,
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self.tr("Expression"), parent_layer=self.INPUT))
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self.addOutput(OutputVector(self.OUTPUT, self.tr('Extracted (expression)')))
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def processAlgorithm(self, context, feedback):
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layer = QgsProcessingUtils.mapLayerFromString(self.getParameterValue(self.INPUT), context)
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expression_string = self.getParameterValue(self.EXPRESSION)
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writer = self.getOutputFromName(self.OUTPUT).getVectorWriter(layer.fields(), layer.wkbType(), layer.crs(),
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context)
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expression = QgsExpression(expression_string)
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if not expression.hasParserError():
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req = QgsFeatureRequest().setFilterExpression(expression_string)
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else:
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raise GeoAlgorithmExecutionException(expression.parserErrorString())
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for f in layer.getFeatures(req):
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writer.addFeature(f)
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del writer
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