SELECT count(DISTINCT party_name) FROM party
Count the number of different parties.
[Schema (values) (types)]: | party_people |  region : region_id (text) , region_name (number) , date (text) , label (text) , format (text) , catalogue (text) | party : party_id (text) , minister (number) , took_office (text) , left_office (text) , region_id (text) , party_name (text) | member : member_id (text) , member_name (number) , party_id (text) , in_office (text) | party_events : event_id (text) , event_name (number) , party_id (text) , member_in_charge_id (text);