Oleg Broytmann wrote: > Hello! > > (This seems like a "developing with Python" question and partially it is > but please read on.) > > I have a class that represents SQL queries. Instances of the class can > be iterated over. ... users of > the class sometimes write > > if sqlQuery: > for row in sqlQuery: ... > else: > # no rows > > To prevent users from writing such code the class implements __nonzero__() > that always raises an exception.
I'm not sure I like that idea. It's common practice to write 'if x:' as a shorthand for 'if x is not None:' when it's known that x is an object that doesn't have a notion of emptiness. A __nonzero__ that always raises an exception just to spite you interferes with that. Another thing is that any code doing "if x" to test for emptiness is clearly expecting x to be a sequence, *not* an iterator, and you've violated the contract by passing it one. This is what you may be running into with the libraries you mention. Generally I think it's a bad idea to try to protect people from themselves when doing so can interfere with legitimate usage. -- Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | Carpe post meridiem! | Christchurch, New Zealand | (I'm not a morning person.) | [EMAIL PROTECTED] +--------------------------------------+ _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
