[chaley]

I think you want something like this ids_for_field() function. I don't know if the order is right. This produces (id, name) but you might want (name, id).

python:

def ids_for_field(db, ids_of_books, field_name):
	# First get all the names for the desired books.
	# Use a set to make them unique
	unique_names = set()
	for tup in db.all_field_for(field_name, ids_of_books).values():
		for vals in tup:
			unique_names.update((vals,))
	# Now get the ids for the names and build the pairs
	id_field_pairs = list()
	for aut in unique_names:
		id_field_pairs.append((db.get_item_id(field_name, aut), aut))
	return id_field_pairs

def evaluate(book, context):
	db = context.db.new_api
	print('--------------------')
	# Get the list of books in the current VL
	ids_in_vl = db.search('', restriction='authors:a')
	# Get the id,val pairs for the desired field
	field_pairs = ids_for_field(db, ids_in_vl, 'authors')
	print(field_pairs) 
	return ''

NB: I am using the python template facility to test the code, which is why "python:" and "def evaluate()" are there. It hadn't occurred to me when we added it that one use is interactive python code debugging inside calibre.