本文整理汇总了Python中qgis.core.QgsVectorLayer.addExpressionField方法的典型用法代码示例。如果您正苦于以下问题：Python QgsVectorLayer.addExpressionField方法的具体用法？Python QgsVectorLayer.addExpressionField怎么用？Python QgsVectorLayer.addExpressionField使用的例子？那么恭喜您, 这里精选的方法代码示例或许可以为您提供帮助。您也可以进一步了解该方法所在类qgis.core.QgsVectorLayer的用法示例。
在下文中一共展示了QgsVectorLayer.addExpressionField方法的6个代码示例，这些例子默认根据受欢迎程度排序。您可以为喜欢或者感觉有用的代码点赞，您的评价将有助于系统推荐出更棒的Python代码示例。
示例1: test_ExpressionFieldNestedGeometry
# 需要导入模块: from qgis.core import QgsVectorLayer [as 别名]
# 或者: from qgis.core.QgsVectorLayer import addExpressionField [as 别名]
def test_ExpressionFieldNestedGeometry(self):
myShpFile = os.path.join(TEST_DATA_DIR, 'points.shp')
layer = QgsVectorLayer(myShpFile, 'Points', 'ogr')
self.assertTrue(layer.isValid())
idx = layer.addExpressionField('$x*2', QgsField('exp1', QVariant.LongLong)) # NOQA
idx = layer.addExpressionField('"exp1"/1.5', QgsField('exp2', QVariant.LongLong)) # NOQA
fet = next(layer.getFeatures(QgsFeatureRequest().setFlags(QgsFeatureRequest.NoGeometry).setSubsetOfAttributes(['exp2'], layer.fields())))
# nested virtual fields should have made geometry be fetched
self.assertEqual(fet['exp2'], -156)
self.assertEqual(fet['exp1'], -234)示例2: test_ExpressionFieldNested
# 需要导入模块: from qgis.core import QgsVectorLayer [as 别名]
# 或者: from qgis.core.QgsVectorLayer import addExpressionField [as 别名]
def test_ExpressionFieldNested(self):
myShpFile = os.path.join(TEST_DATA_DIR, 'points.shp')
layer = QgsVectorLayer(myShpFile, 'Points', 'ogr')
self.assertTrue(layer.isValid())
idx = layer.addExpressionField('"Staff"*2', QgsField('exp1', QVariant.LongLong)) # NOQA
idx = layer.addExpressionField('"exp1"-1', QgsField('exp2', QVariant.LongLong)) # NOQA
fet = next(layer.getFeatures(QgsFeatureRequest().setSubsetOfAttributes(['exp2'], layer.fields())))
self.assertEqual(fet['Class'], NULL)
# nested virtual fields should make all these attributes be fetched
self.assertEqual(fet['Staff'], 2)
self.assertEqual(fet['exp2'], 3)
self.assertEqual(fet['exp1'], 4)示例3: test_ExpressionFieldNestedCircular
# 需要导入模块: from qgis.core import QgsVectorLayer [as 别名]
# 或者: from qgis.core.QgsVectorLayer import addExpressionField [as 别名]
def test_ExpressionFieldNestedCircular(self):
""" test circular virtual field definitions """
myShpFile = os.path.join(TEST_DATA_DIR, 'points.shp')
layer = QgsVectorLayer(myShpFile, 'Points', 'ogr')
self.assertTrue(layer.isValid())
cnt = layer.pendingFields().count() # NOQA
idx = layer.addExpressionField('"exp3"*2', QgsField('exp1', QVariant.LongLong)) # NOQA
idx = layer.addExpressionField('"exp1"-1', QgsField('exp2', QVariant.LongLong)) # NOQA
idx = layer.addExpressionField('"exp2"*3', QgsField('exp3', QVariant.LongLong)) # NOQA
# really just testing that this doesn't hang/crash... there's no good result here!
fet = next(layer.getFeatures(QgsFeatureRequest().setSubsetOfAttributes(['exp2'], layer.fields())))
self.assertEqual(fet['Class'], NULL)示例4: test_ExpressionFieldEllipsoidLengthCalculation
# 需要导入模块: from qgis.core import QgsVectorLayer [as 别名]
# 或者: from qgis.core.QgsVectorLayer import addExpressionField [as 别名]
def test_ExpressionFieldEllipsoidLengthCalculation(self):
#create a temporary layer
temp_layer = QgsVectorLayer("LineString?crs=epsg:3111&field=pk:int", "vl", "memory")
self.assertTrue(temp_layer.isValid())
f1 = QgsFeature(temp_layer.dataProvider().fields(), 1)
f1.setAttribute("pk", 1)
f1.setGeometry(QgsGeometry.fromPolyline([QgsPoint(2484588, 2425722), QgsPoint(2482767, 2398853)]))
temp_layer.dataProvider().addFeatures([f1])
# set project CRS and ellipsoid
srs = QgsCoordinateReferenceSystem(3111, QgsCoordinateReferenceSystem.EpsgCrsId)
QgsProject.instance().writeEntry("SpatialRefSys", "/ProjectCRSProj4String", srs.toProj4())
QgsProject.instance().writeEntry("SpatialRefSys", "/ProjectCRSID", srs.srsid())
QgsProject.instance().writeEntry("SpatialRefSys", "/ProjectCrs", srs.authid())
QgsProject.instance().writeEntry("Measure", "/Ellipsoid", "WGS84")
QgsProject.instance().writeEntry("Measurement", "/DistanceUnits", QgsUnitTypes.encodeUnit(QGis.Meters))
idx = temp_layer.addExpressionField('$length', QgsField('length', QVariant.Double)) # NOQA
# check value
f = temp_layer.getFeatures().next()
expected = 26932.156
self.assertAlmostEqual(f['length'], expected, 3)
# change project length unit, check calculation respects unit
QgsProject.instance().writeEntry("Measurement", "/DistanceUnits", QgsUnitTypes.encodeUnit(QGis.Feet))
f = temp_layer.getFeatures().next()
expected = 88360.0918635
self.assertAlmostEqual(f['length'], expected, 3)示例5: test_ExpressionFieldEllipsoidAreaCalculation
# 需要导入模块: from qgis.core import QgsVectorLayer [as 别名]
# 或者: from qgis.core.QgsVectorLayer import addExpressionField [as 别名]
def test_ExpressionFieldEllipsoidAreaCalculation(self):
#create a temporary layer
temp_layer = QgsVectorLayer("Polygon?crs=epsg:3111&field=pk:int", "vl", "memory")
self.assertTrue(temp_layer.isValid())
f1 = QgsFeature(temp_layer.dataProvider().fields(), 1)
f1.setAttribute("pk", 1)
f1.setGeometry(QgsGeometry.fromPolygon([[QgsPoint(2484588, 2425722), QgsPoint(2482767, 2398853), QgsPoint(2520109, 2397715), QgsPoint(2520792, 2425494), QgsPoint(2484588, 2425722)]]))
temp_layer.dataProvider().addFeatures([f1])
# set project CRS and ellipsoid
srs = QgsCoordinateReferenceSystem(3111, QgsCoordinateReferenceSystem.EpsgCrsId)
QgsProject.instance().writeEntry("SpatialRefSys", "/ProjectCRSProj4String", srs.toProj4())
QgsProject.instance().writeEntry("SpatialRefSys", "/ProjectCRSID", srs.srsid())
QgsProject.instance().writeEntry("SpatialRefSys", "/ProjectCrs", srs.authid())
QgsProject.instance().writeEntry("Measure", "/Ellipsoid", "WGS84")
QgsProject.instance().writeEntry("Measurement", "/AreaUnits", QgsUnitTypes.encodeUnit(QgsUnitTypes.SquareMeters))
idx = temp_layer.addExpressionField('$area', QgsField('area', QVariant.Double)) # NOQA
# check value
f = temp_layer.getFeatures().next()
expected = 1009089817.0
self.assertAlmostEqual(f['area'], expected, delta=1.0)
# change project area unit, check calculation respects unit
QgsProject.instance().writeEntry("Measurement", "/AreaUnits", QgsUnitTypes.encodeUnit(QgsUnitTypes.SquareMiles))
f = temp_layer.getFeatures().next()
expected = 389.6117565069
self.assertAlmostEqual(f['area'], expected, 3)示例6: test_JoinUsingExpression2
# 需要导入模块: from qgis.core import QgsVectorLayer [as 别名]
# 或者: from qgis.core.QgsVectorLayer import addExpressionField [as 别名]
def test_JoinUsingExpression2(self):
""" test joining a layer using a virtual field (the other way!) """
joinLayer = QgsVectorLayer(
"Point?field=x:string&field=y:integer&field=z:integer",
"joinlayer", "memory")
pr = joinLayer.dataProvider()
f1 = QgsFeature()
f1.setAttributes(["foo", 246, 321])
f2 = QgsFeature()
f2.setAttributes(["bar", 456, 654])
self.assertTrue(pr.addFeatures([f1, f2]))
joinLayer.addExpressionField('"y"/2', QgsField('exp1', QVariant.LongLong))
layer = QgsVectorLayer("Point?field=fldtxt:string&field=fldint:integer",
"addfeat", "memory")
pr = layer.dataProvider()
f = QgsFeature()
f.setAttributes(["test", 123])
self.assertTrue(pr.addFeatures([f]))
QgsProject.instance().addMapLayers([layer, joinLayer])
join = QgsVectorLayerJoinInfo()
join.setTargetFieldName("fldint")
join.setJoinLayer(joinLayer)
join.setJoinFieldName("exp1")
join.setUsingMemoryCache(True)
layer.addJoin(join)
f = QgsFeature()
fi = layer.getFeatures()
self.assertTrue(fi.nextFeature(f))
attrs = f.attributes()
self.assertEqual(attrs[0], "test")
self.assertEqual(attrs[1], 123)
self.assertEqual(attrs[2], "foo")
self.assertEqual(attrs[3], 246)
self.assertEqual(attrs[4], 321)
self.assertFalse(fi.nextFeature(f))
QgsProject.instance().removeMapLayers([layer.id(), joinLayer.id()])