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Since it's safe to evaluate parameters in background threads now, it's usually going to be ok to evaluate everything in the processAlgorithm step. This keeps the algorithm code as simple as possible, and will make porting faster. Note that the prepare/postProcess virtual methods still exist and can be used when an algorithm MUST do setup/cleanup work in the main thread.
90 lines
3.5 KiB
Python
90 lines
3.5 KiB
Python
# -*- coding: utf-8 -*-
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"""
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***************************************************************************
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SelectByExpression.py
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---------------------
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Date : July 2014
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Copyright : (C) 2014 by Michael Douchin
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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__ = 'Michael Douchin'
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__date__ = 'July 2014'
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__copyright__ = '(C) 2014, Michael Douchin'
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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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QgsVectorLayer,
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QgsProcessingParameterVectorLayer,
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QgsProcessingParameterExpression,
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QgsProcessingParameterEnum,
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QgsProcessingOutputVectorLayer)
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from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
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from processing.algs.qgis.QgisAlgorithm import QgisAlgorithm
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class SelectByExpression(QgisAlgorithm):
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INPUT = 'INPUT'
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EXPRESSION = 'EXPRESSION'
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OUTPUT = 'OUTPUT'
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METHOD = 'METHOD'
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def group(self):
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return self.tr('Vector selection tools')
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def __init__(self):
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super().__init__()
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self.methods = [self.tr('creating new selection'),
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self.tr('adding to current selection'),
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self.tr('removing from current selection'),
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self.tr('selecting within current selection')]
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self.addParameter(QgsProcessingParameterVectorLayer(self.INPUT, self.tr('Input layer')))
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self.addParameter(QgsProcessingParameterExpression(self.EXPRESSION,
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self.tr('Expression'), parentLayerParameterName=self.INPUT))
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self.addParameter(QgsProcessingParameterEnum(self.METHOD,
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self.tr('Modify current selection by'), self.methods, 0))
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self.addOutput(QgsProcessingOutputVectorLayer(self.OUTPUT, self.tr('Selected (attribute)')))
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def name(self):
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return 'selectbyexpression'
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def displayName(self):
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return self.tr('Select by expression')
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def processAlgorithm(self, parameters, context, feedback):
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layer = self.parameterAsVectorLayer(parameters, self.INPUT, context)
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method = self.parameterAsEnum(parameters, self.METHOD, context)
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if method == 0:
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behavior = QgsVectorLayer.SetSelection
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elif method == 1:
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behavior = QgsVectorLayer.AddToSelection
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elif method == 2:
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behavior = QgsVectorLayer.RemoveFromSelection
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elif method == 3:
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behavior = QgsVectorLayer.IntersectSelection
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expression = self.parameterAsString(parameters, self.EXPRESSION, context)
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qExp = QgsExpression(expression)
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if qExp.hasParserError():
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raise GeoAlgorithmExecutionException(qExp.parserErrorString())
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layer.selectByExpression(expression, behavior)
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return {self.OUTPUT: parameters[self.INPUT]}
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