[web2py] About unary operator consistency in queries
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.id3)).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.id0 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? -- --- 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.
Re: [web2py] About unary operator consistency in queries
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.id3)).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.id0 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.
Re: [web2py] About unary operator consistency in queries
A similar caveat applies to the use of | or in queries. Ok, thanks for the tips Marin and Jonathan. I assume then that the book's example should use parenthesis for negation, since web2py cannot change the Python operator precedence. -- --- 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.
Re: [web2py] About unary operator consistency in queries
On 29 Jan 2013, at 9:42 AM, Alan Etkin spame...@gmail.com wrote: A similar caveat applies to the use of | or in queries. Ok, thanks for the tips Marin and Jonathan. I assume then that the book's example should use parenthesis for negation, since web2py cannot change the Python operator precedence. Yes. Instead of: rows = db((~db.person.name=='Alex') | (db.person.id3)).select() it should read: rows = db(~(db.person.name=='Alex') | (db.person.id3)).select() -- --- 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.
Re: [web2py] About unary operator consistency in queries
On 29 Jan 2013, at 9:46 AM, Jonathan Lundell jlund...@pobox.com wrote: On 29 Jan 2013, at 9:42 AM, Alan Etkin spame...@gmail.com wrote: A similar caveat applies to the use of | or in queries. Ok, thanks for the tips Marin and Jonathan. I assume then that the book's example should use parenthesis for negation, since web2py cannot change the Python operator precedence. Yes. Instead of: rows = db((~db.person.name=='Alex') | (db.person.id3)).select() it should read: rows = db(~(db.person.name=='Alex') | (db.person.id3)).select() I pushed a fix, along with adding a note to the existing note on operator precedence. -- --- 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.
