qgis - How to select features using an expression with pyqgis?

How can I select features with pyqgis using an expression?

I tried to use an QgsExpression but the select method doesn't take it:

exp = QgsExpression("'ogc_fid' = 482")

cLayer = canvas.currentLayer()
cLayer.select(exp)

Is it possible and if so, how do I do it?

Answer

Follow these steps:

1. 
   

   Get the layer reference:

   
   

   cLayer = iface.mapCanvas().currentLayer()

   
   
   


2. 
   

   Get a featureIterator from an expression:

   
   

   expr = QgsExpression( "\"ogc_fid\"=482" )

   
   

   it = cLayer.getFeatures( QgsFeatureRequest( expr ) )

   
   


3. 
   

   Build a list of feature Ids from the result obtained in 2.:

   
   

   ids = [i.id() for i in it]

   
   



4. 
   

   Select features with the ids obtained in 3.:

   
   

   cLayer.setSelectedFeatures( ids )

   
   

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NOTE: If you want to set an expression with a string value, you need to add quotation marks to such value, in this way:

expr = QgsExpression( " \"name\" = 'my string' " )

If your string value comes from a variable, you can do this:

myVariable = 'my string'
expr = QgsExpression( " \"name\" = '{}' ".format(myVariable) )