> Perhaps you meant this? > > assert isinstance(user, User) Yes I meant this,sorry,my mistake.
------------------------ Thx for your and Ben's feedbacks first,it's appreciated. your points is taken by me,but I want to make my opinion more clearly. The assertion is JUST show to my function callers during development,warning that "I want a list/tuple,not some other objects"(BTW, your practice of wrapping arguments to iter is good,I'll take this to improve my code,thx again.).And assertion's off when running Python with the -O (optimize) switch is what I expect,it isn't necessary in production code.Argument validation is done by constuctor of object which I used in assertion. I also have a few words about duck-typing.Duck-typing is good,but how about if I offer a convenient way to my function user by producing or changing what he want to pass me to a *real* duck?Is that more explicit to my user? Anyway,I'll look at my principles which may need some changes or improvements. -- http://mail.python.org/mailman/listinfo/python-list
