I want to search on number values (>, = etc.) within a column and open table for the selected ones. It's an easy task within field calculator, but I want to see how it's build up with the python syntax and then run it. It would help me understand. Or should I run it with the consols editor?

While this is an expression by the attribute (population) i won't need the feature-class, right?

What I want is something like this:

def "population" < 2000

def showAttributeTable() (but only for the selected ones)

There's various way how to do it and depends on what you want.

Solution 1 : with selection assuming you've already select your features :

# My layer test
Layer=QgsVectorLayer("path/to/shapefile.shp","Display name", "ogr")
# list of selected features
selected_features = [ feature for feature in layer.selectedFeatures()]

Solution 2 : with the querie builder :

# My layer test
Layer=QgsVectorLayer("path/to/shapefile.shp","Display name", "ogr")
# set a querie like querie builder in properties
Layer.setSubsetString(u'"population" < 2000')
list_of_features = [feature for feature in layer.getFeatures()]
# reset the querie

I would use the first one for spatial selection and the other one for queries on attributs field

  • Thanks, but that doesn´t generate any output. Instead of first line I suggest I could use: layer = iface.activeLayer() – CARTOS Jan 22 '16 at 11:38

Great answer by @SIGIS! You could also use the following to set your current layer, set the expression and load the Attributes Table with the selected features:

layer = qgis.utils.iface.activeLayer()
exp = QgsExpression( "\"population\"< 2000" )
ids = [i.id() for i in layer.getFeatures(QgsFeatureRequest(exp))]
  • 1
    That´s more like it. Joesph although finishes it with the rest. Thanks to both of you. – CARTOS Jan 22 '16 at 12:00
  • @MORCKANIAS - Most welcome buddy! I find using multiple answers and mixing them up helps me understand how python syntax works =) – Joseph Jan 22 '16 at 12:03
  • 1
    Yeah @Joseph I missed this part to show off attributes. Glad it help. – SIGIS Jan 22 '16 at 12:30
  • @SIGIS - Haha don't worry, I tend to miss things too, but you got the main question answered anyway :) – Joseph Jan 22 '16 at 12:33

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