[processing] added 'Select by expression' algorithm (by Michaël Douchin - 3Liz)

Author: volaya

python/plugins/processing/algs/qgis/QGISAlgorithmProvider.py

@@ -101,6 +101,7 @@
 from ImportIntoPostGIS import ImportIntoPostGIS
 from SetVectorStyle import SetVectorStyle
 from SetRasterStyle import SetRasterStyle
+from SelectByExpression import SelectByExpression
 # from VectorLayerHistogram import VectorLayerHistogram
 # from VectorLayerScatterplot import VectorLayerScatterplot
 # from MeanAndStdDevPlot import MeanAndStdDevPlot
@@ -157,7 +158,7 @@ def __init__(self):
                         RandomPointsPolygonsVariable(),
                         RandomPointsAlongLines(), PointsToPaths(),
                         PostGISExecuteSQL(), ImportIntoPostGIS(),
-                        SetVectorStyle(), SetRasterStyle(),
+                        SetVectorStyle(), SetRasterStyle(), SelectByExpression()
                         # ------ raster ------
                         # CreateConstantRaster(),
                         # ------ graphics ------

python/plugins/processing/algs/qgis/SelectByExpression.py

@@ -0,0 +1,80 @@
+# -*- coding: utf-8 -*-
+
+"""
+***************************************************************************
+    SelectByExpression.py
+    ---------------------
+    Date                 : July 2014
+    Copyright            : (C) 2014 by Michaël Douchin
+***************************************************************************
+*                                                                         *
+*   This program is free software; you can redistribute it and/or modify  *
+*   it under the terms of the GNU General Public License as published by  *
+*   the Free Software Foundation; either version 2 of the License, or     *
+*   (at your option) any later version.                                   *
+*                                                                         *
+***************************************************************************
+"""
+
+__author__ = 'Michael Douchin'
+__date__ = 'July 2014'
+__copyright__ = '(C) 2014, Michael Douchin'
+
+# This will get replaced with a git SHA1 when you do a git archive
+
+__revision__ = '$Format:%H$'
+
+import processing
+from qgis.core import *
+from processing.core.GeoAlgorithmExecutionException import GeoAlgorithmExecutionException
+from processing.parameters.ParameterVector import ParameterVector
+from processing.parameters.ParameterSelection import ParameterSelection
+from processing.outputs.OutputVector import OutputVector
+from processing.core.GeoAlgorithm import GeoAlgorithm
+from processing.parameters.ParameterString import ParameterString
+
+class SelectByExpression(GeoAlgorithm):
+
+    LAYERNAME = 'LAYERNAME'
+    EXPRESSION= 'EXPRESSION'
+    RESULT = 'RESULT'
+    METHOD = 'METHOD'
+    METHODS = ['creating new selection', 'adding to current selection',
+               'removing from current selection']
+
+    def defineCharacteristics(self):
+        self.name = 'Select by expression'
+        self.group = 'Vector selection tools'
+
+        self.addParameter(ParameterVector(self.LAYERNAME, 'Input Layer',
+                          [ParameterVector.VECTOR_TYPE_ANY]))
+        self.addParameter(ParameterString(self.EXPRESSION, "Expression"))
+        self.addParameter(ParameterSelection(self.METHOD,
+                          'Modify current selection by', self.METHODS, 0))
+        self.addOutput(OutputVector(self.RESULT, 'Output', True))
+
+    def processAlgorithm(self, progress):
+
+        filename = self.getParameterValue(self.LAYERNAME)
+        layer = processing.getObject(filename)
+        oldSelection = set(layer.selectedFeaturesIds())
+        method = self.getParameterValue(self.METHOD)
+
+        # Build QGIS request with expression
+        expression = self.getParameterValue(self.EXPRESSION)
+        qExp = QgsExpression(expression)
+        if not qExp.hasParserError():
+            qReq = QgsFeatureRequest(qExp)
+        else:
+            raise GeoAlgorithmExecutionException(qExp.parserErrorString())
+        selected = [f.id() for f in layer.getFeatures(qReq)]
+
+        if method == 1:
+            selected = list(oldSelection.union(selected))
+        elif method == 2:
+            selected = list(oldSelection.difference(selected))
+
+        # Set the selection
+        layer.setSelectedFeatures(selected)
+
+        self.setOutputValue(self.RESULT, filename)