qgis - How to access a specific feature?

Is it possible to go to a specified row number (or perhaps the next/previous) row using PyQGIS?

This code gets the value of the first attribute in the first row of the table

features = aLayer.getFeatures()
attrs = feat.attributes()
attribute0 = attrs[0]
print attribute0

How can I get the value of the same column (0), for row 2, 22, 222...? Is there a way to do this without using a for loop?

Answer

You could access the specific feature, without a loop, using the setFilterFid() method.

In your case, if you wanted to call the feature in row 222, you would do:

aLayer = iface.activeLayer()


request = QgsFeatureRequest().setFilterFid(222)
feat = aLayer.getFeatures(request).next()
print feat.attributes()

To just get a specific attribute, you would use

feat['COLUM_NAME']

or

feat.attributes()[INDEX]

instead of feat.attributes() in the snippet above.