QGIS » QGIS Application

#!/usr/bin/env python

import sys

import time

from qgis.core import *

composedURI = '/tmp/test-sqlite/p.sqlite|layername=p'

layer = QgsVectorLayer(composedURI, 'p', 'ogr')

features = layer.getFeatures()

fieldID = layer.fieldNameIndex('value')

start = time.time()

layer.startEditing()

layer.updateFields()

for feature in features:

    featureID = feature.id()

    layer.changeAttributeValue(featureID, fieldID, -1)

layer.commitChanges()

print ("Time elapsed: {}".format(time.time() - start))