2

I'd like to be able to split the parcel information in an attribute table from one column

parcel_value = 247/34

into two separated columns by using a PyScript

parcel_num = 247

and

parcel_den = 34

I was starting with this but then ran out of knowledge:

layer = iface.activeLayer()
for field in layer.fields():
    if field.name() == 'parcel_value':
        with edit(layer):
            idx = layer.fields().indexFromName(field.name())
            layer.renameAttribute(idx, 'parcel_num')
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2 Answers 2

Reset to default
2

You can use the code snippet below. Instead of renaming and updating the "parcel_value" field, I would recommend adding two new integer fields, since after splitting the attribute values, you now have numeric data, and should store it as such.

layer = iface.activeLayer()
layer.dataProvider().addAttributes([QgsField('parcel_num', QVariant.Int), QgsField('parcel_den', QVariant.Int)])
layer.updateFields()
num_idx = layer.fields().lookupField('parcel_num')
den_idx = layer.fields().lookupField('parcel_den')

att_map = {}

for f in layer.getFeatures():
    if f['parcel_value'] != NULL:
        att_split = f['parcel_value'].split('/')
        num = att_split[0]
        den = NULL
        if len(att_split) == 2:
            if att_split[1]:
                den = att_split[1]
        att_map[f.id()] = {num_idx: num, den_idx: den}
    
layer.dataProvider().changeAttributeValues(att_map)

# Uncomment lines below to delete the original field (personally, I would leave it but it's up to you)

#layer.dataProvider().deleteAttributes([layer.fields().lookupField('parcel_value')])
#layer.updateFields()

Result:

enter image description here

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3
  • 1
    And if you want to change something later on, or something goes wrong, you still have your original data to work with :)
    – Matt
    Commented Nov 10, 2022 at 6:09
  • @Ben W: i forgot to mention, that in some cases there is no denominator in the parcel_value column. In that case the value of the parcel_value should land in 'parcel_num'. without adressing that problem, the results are NULL. Otherwise it works perfectly.
    – Marek
    Commented Nov 10, 2022 at 17:30
  • @Marek, see my updated answer which will cover the case you describe.
    – Ben W
    Commented Nov 10, 2022 at 23:20
2

If you have already set the column names of parcel_num and parcel_den in the attribute table, you can run the following code which will extract values before and after the forward slash / into separate columns. The code assumes the column types of the parcel_num and parcel_den are integers.

layer = iface.activeLayer()

with edit(layer):
    for feature in layer.getFeatures():
        value = feature['parcel_val'] # update the field name of the parcel_value 
        print(value)
        feature['parcel_num'] = value.split('/')[0]
        feature['parcel_den'] = value.split('/')[1]
        layer.updateFeature(feature)

Before running the code:

enter image description here

After running the code:

enter image description here

Without PyQGIS, you can also achieve the same results using Field Calculator:

  • Check Update Existing Field and select parcel_num

  • Write the following expression

     regexp_replace("parcel_val" ,'(\\d+)/(\\d+)','\\1')

Do the same steps for parcel_den

  • Check Update Existing Field and select parcel_den

  • Write the following expression

     regexp_replace("parcel_val" ,'(\\d+)/(\\d+)','\\2')

Where parcel_val is the name of the field that holds the parcel values, for example, 247/34.

You will get the same results as before.

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