Deleting duplicate records in the attribute table and keep the minimum value in PyQGIS?

Question

I have two fields: ID_PARCEL and NL. The ID_PARCEL is the field that contains duplicate records. I would like to remove the duplicate record by keeping the minimum NL field value. For example: the value 22 in the ID_PARCEL field is duplicated, so the row of the attributes table that should be removed is the one with the highest value in the NL field, which in this case is the value 627.

I searched on the site, but what I found was deleting duplicate records without the condition to keep the minimum value of another field. Can someone help me?

Answer 1

If I understand your question, you may use the following code:

layer= iface.activeLayer() # load the layer as you want
vals = {} # create an empty dictionary

# Let's populate the dictionary
for feat in layer.getFeatures():
    if feat['ID_PARCEL'] not in vals:
        vals[feat['ID_PARCEL']] = [feat['NL']]
    else:
        vals[feat['ID_PARCEL']].append(feat['NL'])

# Let's find the minimum value from the "NL" field for each "ID_PARCEL" field
for key, value in vals.iteritems():
    vals[key] = min(value)

# Let's delete the unwanted features
with edit(layer):
    for feature in layer.getFeatures():
        k = feature['ID_PARCEL']
        if feature['NL'] != vals[k]:
            layer.deleteFeature(feature.id())

Since the edits will apply immediately, please create a backup copy of the original data before running the above code.