QGIS feature value unexpectedly not changing

Question

I am using this code in the QGIS Python console to update a feature value. However, in order to get the feature value to change, I have to run it twice. Suggestions on why this is happening?

layer = iface.activeLayer()

layerFields = layer.fields()
fieldIndex = layerFields.indexFromName("February")
feature = layer.selectedFeatures()
featureID = feature[0].id()
label = 'G'
layer.startEditing()
layer.changeAttributeValue(featureID, fieldIndex, label)
layer.commitChanges()

print(fieldIndex)

for f in feature:
    print(f.attributes())

1st:

    exec(open('C:/..../AppData/Local/Temp/tmpb78pyjoe.py'.encode('utf- 8')).read())
    3
    [10, 440631, NULL, NULL]

2nd:

    exec(open('C:/..../AppData/Local/Temp/tmp_9u0wl9z.py'.encode('utf-8')).read())
    3
    [10, 440631, NULL, 'G']

Answer 1

You need to get your Features again, with the updated values. Otherwise you will get them from memory, where you stored it before you have done your changes. Add

feature = layer.selectedFeatures()

before you print the attribute values.

layer = iface.activeLayer()

layerFields = layer.fields()
fieldIndex = layerFields.indexFromName("February")
feature = layer.selectedFeatures()
featureID = feature[0].id()
label = 'G'
layer.startEditing()
layer.changeAttributeValue(featureID, fieldIndex, label)
layer.commitChanges()

print(fieldIndex)

feature = layer.selectedFeatures()

for f in feature:
    print(f.attributes())