Export only specific fields of a QGIS layer as CSV

Question

I have some layers that contain attachments (photos and videos). The layers have the following attributes: ['ATTACHMENTID', 'GLOBALID', 'REL_GLOBALID', 'CONTENT_TYPE', 'ATT_NAME', 'DATA_SIZE', 'DATA'] The attachments are stored in the DATA field. I want to export the attribute table as CSV except the DATA field, as it inflates the field and contains no useful information. I used the following code:

def save_layer_as_csv(layer, save_path, save_name):
    '''Solutions from:https://gis.stackexchange.com/a/373856/95891
                  and:https://gis.stackexchange.com/a/348457/95891'''

    QgsVectorFileWriter.writeAsVectorFormat(layer,f'{save_path}/{save_name}.csv',
    "utf-8",driverName = "CSV" , layerOptions = ['GEOMETRY=AS_XYZ'])

This code exports all the fields which are not needed. I found a good post here that exports only one field of the layer by adding attributes=[idx], onlySelected=True to the line above, but I don't know how to slice the fields as object and add them to the attribute parameter!

I tried to slice using the layer.fields()[:-1] code, but it returned an error argument 1 has unexpected type 'slice'

How can I solve this issue to export all the fields except the last one?

Note: I use QGIS 3.26.2-Buenos Aires

Answer 1

You can construct indices' list.

fields = ['ATTACHMENTID', 'GLOBALID', 'REL_GLOBALID',
          'CONTENT_TYPE', 'ATT_NAME', 'DATA_SIZE'] 
idxs = [layer.fields().indexFromName(f) for f in fields]

And use attributes=idxs instead of attributes=[idx] as parameter.

Answer 2

layer.fileds() returns a QgsFields object, not a list. If you need to omit the last field, use this:

idxs = list(range(len(layer.fields())- 1))

And use attributes=idxs.