[Noughty]

And I just wrote

return ', '.join(sorted(res))

Is it wrong? The result seems to be correct...

Where could I read more about functions in python?

Seems the speed increased by half a minute. Maybe I could make other columns like this too (genre, character). Since they are basically the same it might not be hard.

def evaluate(self, formatter, kwargs, mi, locals):
	# Tags is a multiple text field, so it is already split
	tags = set(mi.get('tags', []))
	# Shelf is a composite column, so we must split it
	shelf = set([l.strip() for l in mi.get('#shelf', "").split(',')])
	
	# items to remove from the result
	to_remove = set(['Short', 'delete', 'foo', 'bar', somethingElse',
		 'andSoOn', 'until I get tired', 'of adding things']) 

	# combine the two fields containing items we might want to keep.
	st = tags | shelf
	# now remove the items we don't want in the result
	res = st - to_remove
	return ', '.join(res)

I need another function. I need to leave the values I list, not remove them. For example I am doing the genre column, so I would list all genre values I have in my library, so in the returned list only they remain.

I need to extract specific values