>
> def view():
> postid = request.args(0)
> post = db(db.blogPost.id == postid).select()[0]
>
When the postid doesn't exist, the above select will return an empty Rows
object, so subscripting it with [0] results in the IndexError. The web2py
framework has no way of knowing that this particular Python exception
represents a missing resource and should thus return a 404 response. If a
URL requests an application, controller, function, or static file that
doesn't exist, the framework knows to issue a 404, but general application
code exceptions are treated as 500 server errors by default. If you want,
you can raise your own 404:
post = db(db.blogPost.id == postid).select().first()
if not post:
raise HTTP(404, 'sorry, that post does not exist')
Note, it is better to use .first() to select the first row of the result
because if there are no rows, it will simply return None instead of raising
an exception. If you want a nicer 404 page, you can either use
routes_on_error to catch the 404 and point to either a static file or an
error handling action, or you can directly redirect to an error handling
action instead of raising the HTTP(404). If you create an error handling
action, make sure it sets response.status = 404 before returning so the
browser receives the correct response code with the page.
Anthony
