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Selecting and updating attribute values using Python console in QGIS?



Planned maintenance scheduled April 23, 2019 at 00:00UTC (8:00pm US/Eastern)
Announcing the arrival of Valued Associate #679: Cesar Manara
Unicorn Meta Zoo #1: Why another podcast?“Select by Attribute” in QGIS using python?QGIS plugin select and edit feature attributeUpdating an Open Attribute TableUpdating feature attribute in QGIS plugin?How to get QgsFeatureId with row and column in qtablewidget.(PyQGIS)Feature Selection Using Custom Python Expression Functions in QGIS 2.18QGIS: SQL query within python console to sum a column based on values of other two columnsCannot calculate new values for an empty attribute using existing attributes in QGIS with pythonSelect features using an expression, QGISChange attribute table value using graphical modeler?



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3















I am working with Landusefc and Class columns (ref table).



What I want is: Selecting all water from "Class" and giving a value say '8' in the "Landusefc" column for these selected features.



Table looks like



Test table
I have tried the following code, it works till the selection part but doesn't seem to change the attribute value using the ChangeAttributeValue.



from qgis.core import *
import processing
layer=processing.getObject('test1')
query= ' "class" = 'Water' '
selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query))
layer.setSelectedFeatures([k.id() for k in selection])

#using change Attribute to change the value of the selected feature

layer.startEditing()
for feat in selection:
layer.changeAttributeValue(feat.id(), 5, 8)

layer.commitChanges()









share|improve this question






























    3















    I am working with Landusefc and Class columns (ref table).



    What I want is: Selecting all water from "Class" and giving a value say '8' in the "Landusefc" column for these selected features.



    Table looks like



    Test table
    I have tried the following code, it works till the selection part but doesn't seem to change the attribute value using the ChangeAttributeValue.



    from qgis.core import *
    import processing
    layer=processing.getObject('test1')
    query= ' "class" = 'Water' '
    selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query))
    layer.setSelectedFeatures([k.id() for k in selection])

    #using change Attribute to change the value of the selected feature

    layer.startEditing()
    for feat in selection:
    layer.changeAttributeValue(feat.id(), 5, 8)

    layer.commitChanges()









    share|improve this question


























      3












      3








      3


      1






      I am working with Landusefc and Class columns (ref table).



      What I want is: Selecting all water from "Class" and giving a value say '8' in the "Landusefc" column for these selected features.



      Table looks like



      Test table
      I have tried the following code, it works till the selection part but doesn't seem to change the attribute value using the ChangeAttributeValue.



      from qgis.core import *
      import processing
      layer=processing.getObject('test1')
      query= ' "class" = 'Water' '
      selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query))
      layer.setSelectedFeatures([k.id() for k in selection])

      #using change Attribute to change the value of the selected feature

      layer.startEditing()
      for feat in selection:
      layer.changeAttributeValue(feat.id(), 5, 8)

      layer.commitChanges()









      share|improve this question
















      I am working with Landusefc and Class columns (ref table).



      What I want is: Selecting all water from "Class" and giving a value say '8' in the "Landusefc" column for these selected features.



      Table looks like



      Test table
      I have tried the following code, it works till the selection part but doesn't seem to change the attribute value using the ChangeAttributeValue.



      from qgis.core import *
      import processing
      layer=processing.getObject('test1')
      query= ' "class" = 'Water' '
      selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query))
      layer.setSelectedFeatures([k.id() for k in selection])

      #using change Attribute to change the value of the selected feature

      layer.startEditing()
      for feat in selection:
      layer.changeAttributeValue(feat.id(), 5, 8)

      layer.commitChanges()






      qgis pyqgis select-by-attribute






      share|improve this question















      share|improve this question













      share|improve this question




      share|improve this question








      edited Apr 11 at 7:48









      Kadir Şahbaz

      4,69221531




      4,69221531










      asked Apr 11 at 6:45









      ShellyShelly

      262




      262




















          1 Answer
          1






          active

          oldest

          votes


















          3














          SOLUTION 1:



          You have to remove layer.setSelectedFeatures([k.id() for k in selection]).



          Because selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query)) line gives you a QgsFeatureIterator, that's an iterator. When you use that iterator once, you reach the end of the iterator. Then, if you use it again, you get nothing.



          In your case, when you use selection variable (it's an iterator now) in [k.id() for k in selection], you reach the end. If you use selection in for loop, since you are at the end of the iterator, you don't have any feature now. If you want to be certain, you can add a print("Foo") line to for loop.



          SOLUTION 2:



          Change for feat in selection: into for feat in layer.selectedFeatures():. This solution works only on QGIS 2.x.






          share|improve this answer

























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            1 Answer
            1






            active

            oldest

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            1 Answer
            1






            active

            oldest

            votes









            active

            oldest

            votes






            active

            oldest

            votes









            3














            SOLUTION 1:



            You have to remove layer.setSelectedFeatures([k.id() for k in selection]).



            Because selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query)) line gives you a QgsFeatureIterator, that's an iterator. When you use that iterator once, you reach the end of the iterator. Then, if you use it again, you get nothing.



            In your case, when you use selection variable (it's an iterator now) in [k.id() for k in selection], you reach the end. If you use selection in for loop, since you are at the end of the iterator, you don't have any feature now. If you want to be certain, you can add a print("Foo") line to for loop.



            SOLUTION 2:



            Change for feat in selection: into for feat in layer.selectedFeatures():. This solution works only on QGIS 2.x.






            share|improve this answer





























              3














              SOLUTION 1:



              You have to remove layer.setSelectedFeatures([k.id() for k in selection]).



              Because selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query)) line gives you a QgsFeatureIterator, that's an iterator. When you use that iterator once, you reach the end of the iterator. Then, if you use it again, you get nothing.



              In your case, when you use selection variable (it's an iterator now) in [k.id() for k in selection], you reach the end. If you use selection in for loop, since you are at the end of the iterator, you don't have any feature now. If you want to be certain, you can add a print("Foo") line to for loop.



              SOLUTION 2:



              Change for feat in selection: into for feat in layer.selectedFeatures():. This solution works only on QGIS 2.x.






              share|improve this answer



























                3












                3








                3







                SOLUTION 1:



                You have to remove layer.setSelectedFeatures([k.id() for k in selection]).



                Because selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query)) line gives you a QgsFeatureIterator, that's an iterator. When you use that iterator once, you reach the end of the iterator. Then, if you use it again, you get nothing.



                In your case, when you use selection variable (it's an iterator now) in [k.id() for k in selection], you reach the end. If you use selection in for loop, since you are at the end of the iterator, you don't have any feature now. If you want to be certain, you can add a print("Foo") line to for loop.



                SOLUTION 2:



                Change for feat in selection: into for feat in layer.selectedFeatures():. This solution works only on QGIS 2.x.






                share|improve this answer















                SOLUTION 1:



                You have to remove layer.setSelectedFeatures([k.id() for k in selection]).



                Because selection = layer.getFeatures(QgsFeatureRequest().setFilterExpression(query)) line gives you a QgsFeatureIterator, that's an iterator. When you use that iterator once, you reach the end of the iterator. Then, if you use it again, you get nothing.



                In your case, when you use selection variable (it's an iterator now) in [k.id() for k in selection], you reach the end. If you use selection in for loop, since you are at the end of the iterator, you don't have any feature now. If you want to be certain, you can add a print("Foo") line to for loop.



                SOLUTION 2:



                Change for feat in selection: into for feat in layer.selectedFeatures():. This solution works only on QGIS 2.x.







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited Apr 11 at 9:08

























                answered Apr 11 at 7:46









                Kadir ŞahbazKadir Şahbaz

                4,69221531




                4,69221531



























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