Iterating over features

Now, it's time to discover how to get all the features or a subset of them. The main way to iterate over all features or records of myVector is by using the following code that shows the ID of each feature:

for feature in myVector.getFeatures():
    feature.id()

This will print a list of all the 653 record IDs as shown here:

0L
1L
...[cut]...
652L

It's not always necessary to parse all records to get a subset of them. In this case, we have to set the QgsFeatureRequest class parameters to instruct getFeatures and then retrieve only a subset of records; in some cases, we must also retrieve a subset of columns.

The following code will get only a subset of features and columns:

rect = QgsRectangle(  1223070.695,  2293653.357 , 9046974.211,  4184988.662)

myVector.setSubsetString(' "AREA_MI" > 1000 ')
request =  QgsFeatureRequest()
request.setSubsetOfAttributes([0, 2])
request.setFilterRect( rect )

for index, feature in enumerate( myVector.getFeatures( request ) ):
  ...