python - Understanding intermediary SQL statements in SQLAlchemy -

so have table, , want have users able view table in whichever order they'd like. here's example:

class thing(base):     __tablename__ = 'thing'     id = column(integer, primary_key=true)     amount = column(integer)     date = column(datetime, default=datetime.now())      def __init__(self, amount):         self.amount = amount 

so i'd make following query:

 if sort == 'amount':      orderby = thing.amount.desc()  elif sort == 'date':      orderby = thing.date.desc()   things = dbsession.query(thing).order_by(orderby).all() 

main questions:

1. when set orderby statement, calling or statement being set?
2. am doing correctly , efficiently?

3. can filters?

   filterby = thing.amount == 5

   things = dbsession.query(thing).filter_by(filterby).all()

thanks!

ans 1: when giving syntax return can check type of syntax like

when write

in [5]: thing.amount.desc() out[5]: <sqlalchemy.sql.expression._unaryexpression object @ 0x199a5d0> 

it create 1 object of type expression._unaryexpression. expression can give sqlalchemy when want unary operation. when print in [6]: = thing.amount.desc()

in [7]: print thing.amount desc 

so when query run converted in thing.amount desc. when create expression not call thing, create structure of query.

ans: 2 when creating query create object needed. filter , order need expression if pass directly order_by or filter create object same internally. can use both way.

ans: 3

in [8]: thing.amount == 5 out[8]: <sqlalchemy.sql.expression._binaryexpression object @ 0x1a1dbd0> 

this expression can give expression filter_by.

you more idea expression sqlalchemy site.