# It's easier to store a dict of the possible lookups we want, where
# the values are the keyword arguments for the actual query.
qdict = { 'available_for': 'property__houselet_available_for',
          'available_to_move_in': 'property_available_from',
          'district': 'property__district',
          'furnished': 'property__houselet__furniture_option',
          'max_price': 'property__houselet__rent_price__lte',
          'min_price': 'property__houselet__rent_price__gte',
          'property_type': 'property__property_type'
        }

# Then we can do this all in one step instead of needing to call
# 'filter' and deal with intermediate data structures.
q_objs = [Q(**{qdict[k]: form.clean_data[k]}) for k in qdict.keys() if form.clean_data.get(k, None)]

search_results = Ad.objects.select_related().filter(*q_objs)