Creating empty DBF table and populate it with PyQGIS

Question

I need to create a standalone DBF file with some features. I know how to add the fields but I'm not able to add features and to create only a standalone DBF, without any other files such as .shp or .prj. I've tried creating a LineString in memory and then writing it with QgsVectorFileWriter, using ESRI Shapefile as driver, but it creates a simple shapefile with no features. The GDAL docs say that it can manage standalone DBF but I'm struggling with it and I can't find the way to do it.

This is the code I tried to create it and the export it.

self.work_line_table = QgsVectorLayer('LineString', 'Line_table', 'memory')

[Code for adding fields]

# Add features using the attribute from another layer. It's not working
self.work_line_table.startEditing()
for line in self.work_line_layer.getFeatures():
    line_id = line['IdLinia']
    feature = QgsFeature()
    feature.setAttributes([line_id, self.municipi_codi_ine])
    self.work_line_table.dataProvider().addFeatures([feature])

self.work_line_table.commitChanges()

# Export the table
QgsVectorFileWriter.writeAsVectorFormat(self.work_line_table,
                                        os.path.join(GENERADOR_WORK_DIR, 'MM_LiniesTaula.dbf'),
                                        'utf-8', self.crs, 'ESRI Shapefile')

I've thought in creating it as shapefile and then removing all the other files associated to it except the DBF file, but anyway I can't add any feature to the DBF.

Answer 1

Not sure why you expect a standalone DBF. By default, if you export to a DBF file, you will lose the geometry along the transformation. You may transform the geometry as an "ordinary" attribute e.g like a WKT geometry column to keep the info (in your case line.geometry().asWkt() is a way to get it)

You can find below a standalone recipe to do the job to export to DBF from an existing layer. It will create only a DBF with a CPG file (useful to know the encoding but not used by tools like LibreOffice or Excel, only by tools using OGR/GDAL behind the scene). Adapt it to your case.

layer = iface.activeLayer()
project = QgsProject.instance()
contextProject = project.transformContext()

optionsDbf = QgsVectorFileWriter.SaveVectorOptions()
optionsDbf.driverName = 'DBF file'
QgsVectorFileWriter.writeAsVectorFormatV2 (
    layer,
    '/tmp/myfile.dbf',
    contextProject,
    optionsDbf
)