list attribute has no order by

Question

I tried to do a sorting in sqlalchemy query, the parameters come from 'query_sort' which contains a list of sort parameter (field and direction).

here is the code

      def select_all(self, query_paging, query_sort):
          """ method to select all the transport type"""
          try:
              select_all_query =\
              self._session.query(TransportType)
              for s in query_sort:
                  select_all_query =\
>>                select_all_query.order_by(s.dir(getattr(TransportType,  s.field)))\
                  .limit(query_paging.page_size)\
                  .offset(query_paging.skip)\
                  .all()
              return select_all_query
          except NoResultFound:
              return None

Then in py.test, I tried to test this program by using this code :

s1 = sort
s1.field = "type"
s1.dir = asc

s2 = sort
s2.field = "transport_type_id"
s2.dir = asc

query_sort = [s1,s2]

query_paging.skip = 1
query_paging.page_size = 10
transport_types = repo.select_all(query_paging, query_sort)
assert len(transport_types) == 1

when I ran the test, I got this error :

E               AttributeError: 'list' object has no attribute 'order_by'

It worked fine when I was only using one data (s1) but when I try to test it using more than one data then it produces this error.

Answer 1

You called .all() on your query, which returns all results of the query in a list:

select_all_query =\
select_all_query.order_by(s.dir(getattr(TransportType,  s.field)))\
.limit(query_paging.page_size)\
.offset(query_paging.skip)\
.all()

so the next iteration of the loop select_all_query is now a list.

If you need to apply different orderings, do just that in the loop:

select_all_query = self._session.query(TransportType)
for s in query_sort:
    select_all_query = select_all_query.order_by(
        s.dir(getattr(TransportType,  s.field)))

select_all_query = (
    select_all_query.limit(query_paging.page_size)
                    .offset(query_paging.skip)
                    .all())
return select_all_query

Answer 2

My solution was to change the all().order_by() to filter().order_by()

To order post by recent date posted I did.

posts = Post.query.filter().order_by('date_posted desc')

Hope that helps.