Getting feature count of QgsVectorLayer using PyQGIS?

Question

I'm using this code to get features from QgsVectorLayer

 QgsVectorDataProvider* provider=theVectorLayer->dataProvider();
            if(!provider)
            {
                return;
            }

            theVectorLayer->select(provider->attributeIndexes(),theVectorLayer->extent(),true,false);
    theVectorLayer->selectedFeatureCount();//here returns 0 but there is one polygon
    while(theVectorLayer->nextFeature(currentFeature))
            {
         ....//here Iget attributes and current geometry (one polygon)
            }

How do I get feature count?

Method featureCount() returns -1.

I suggest you check its source, -1 sounds like it encountered an error and then intentionally returned an invalid result. — lynxlynxlynx, Jul 13 '12 at 15:11
The obvious answer would be that the previous select call didn't select anything. Check your parameters. — lynxlynxlynx, Jul 13 '12 at 15:23

score 15 · Accepted Answer · edited Jul 14 '12 at 08:36

15

When featureCount() returns -1 the only safe bet to get the feature count is to iterate over all feature and count them.

selectedFeatureCount() is the number of features that are selected on the layer (e.g. with setSelectedFeatures() or void select(QgsFeatureId featureId, bool emitSignal=true)), but has nothing to do with the select()/nextFeature() combo.

edited Jul 14 '12 at 08:36

unicoletti

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answered Jul 13 '12 at 20:55

jef

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Getting feature count of QgsVectorLayer using PyQGIS?

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