On Aug 22, 10:32 pm, Peter Otten <[EMAIL PROTECTED]> wrote: > Christian Heimes wrote: > > Steven D'Aprano wrote: > >> I suggest that Python should raise warnings.RuntimeWarning (or similar?) > >> when a function is defined with a default argument consisting of a list, > >> dict or set. (This is not meant as an exhaustive list of all possible > >> mutable types, but as the most common ones that I expect will trip up > >> newbies.) The warning should refer to the relevant FAQ or section in the > >> docs. > > >> What do people think? > > -0 from me. I'd rather feature it more prominently in the tutorial, a > section "The five most common pitfalls" or something like that. > > > I don't see a chance for your proposal. How are you going to detect > > mutable objects? Custom types can be mutable as well as immutable. > > A check at compilation time for list literals would catch 90 % of the cases. > The warning would be targeted at newbies after all. It might still be a > source of confusion when they try to import someone else's code that uses > mutable defaults intentionally.
-1. I think, as many people before me has said, we should treat programmers as an adult[1], and doesn't try to babysit them by giving a warning, or worse as an exception. But I do agree that python should have something like -Wall, where programmers are warned of all potential problems. [1] Anyway, you spent your time being a newbie only for a very short time. -- http://mail.python.org/mailman/listinfo/python-list
