On 29 Jan 2013, at 8:50 AM, Alan Etkin <spame...@gmail.com> wrote: > With trunk, I have tested the behavior of the ~ operator, and doesn't seem > consistent to me: > > Here Bruno gives a working example of belongs negation > https://groups.google.com/d/msg/web2py/fCB9a4K9FqU/GBLwfzNnkjMJ > > But the book uses this example: > rows = db((~db.person.name=='Alex') | (db.person.id>3)).select() > > This is wat I get in the console (with SQLite/Python 2.7.3) > > >>> q = ~db.auth_user.id.belongs(1,2,3) > >>> q > <Query (NOT (auth_user.id IN (1,2,3)))> > > >>> q = ~db.auth_user.id==0 > >>> q > <Query (auth_user.id DESC = 0)> > > >>> q = ~db.auth_user.id>0 > >>> q > <Query (auth_user.id DESC > 0)> > >>> q.select() > Traceback (most recent call last): > File "<console>", line 1, in <module> > AttributeError: 'Query' object has no attribute 'select' > >>> db(q).select() > Traceback (most recent call last): > ... > OperationalError: near "DESC": syntax error > > > Note that the second and third query would return an OperationalError (the > INVERT operator is used instead of NOT) > > To avoid the error the syntax must be ~(db.auth_user.id==0), with parethesis. > > Is this an problem with the sqlite adapter only?
It's an issue with the precedence of Python operators. ~ has higher precedence than comparisons, so the parens are required. Python objects can override the functionality of operators, but not their precedence. A similar caveat applies to the use of | or & in queries. -- --- You received this message because you are subscribed to the Google Groups "web2py-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to web2py+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
