[QGIS-Developer] Python and ExpressionContext question

Andreas Neumann a.neumann at carto.net
Fri Dec 1 08:26:26 PST 2017


I am trying to evaluate an expression on a selected feature in my Python

Here is my code: 


selFeature = selectedFeatures[0]
context = QgsExpressionContext()
scope = QgsExpressionContextScope()
exp = QgsExpression('represent_value(routenr)')
routenNameNr = exp.evaluate(context) 


The code above works fine for a "normal" expression, like e.g.
"$length", but it fails for "represent_value(fieldname)". I guess this
is because represent_value involves another layer (relation reference
widget). How could I enhance my code so that
"represent_value(fieldname)" would also work? 

Thanks a lot for your hints! 

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