from django.db import migrations def update_cable_lengths(apps, schema_editor): Cable = apps.get_model('dcim', 'Cable') # Set the absolute length for any zero-length Cables Cable.objects.filter(length=0).update(_abs_length=0) class Migration(migrations.Migration): dependencies = [ ('dcim', '0181_rename_device_role_device_role'), ] operations = [ migrations.RunPython( code=update_cable_lengths, reverse_code=migrations.RunPython.noop ), ]