How to get record by url, insert if not found

I'm doing this currently and getting an error:

Attribute Error 'Table' object has not attribute url

p = session.query(pages.url == someurl).first()

if p is None:
   p = Page()
   p....
   ..
   session.add(p)
   session.commit()


SomeFu开发者_如何转开发nction(p)

I am weary if something returns null my code is going to fail, is it correct?

---

No, your approach is not correct, and the error is not of the 'no row' nature. From the error message, 'pages' is obviously a Table object, and not a class mapped to a table. Either you change the expression to Pages.url==someurl or you use pages.c.url==someurl, thus, specifying that you are looking for a (c) column by the name of url. Still, it is very unclear what you are trying to achieve here.