On Thu, Oct 21, 2010 at 7:53 PM, John Nagle <na...@animats.com> wrote:
> On 10/21/2010 2:51 PM, Chris Rebert wrote: > >> On Thu, Oct 21, 2010 at 2:36 PM, Sean Choi<gne...@gmail.com> wrote: >> >>> I found two similar questions in the mailing list, but I didn't >>> understand >>> >>> the explanations. >>> I ran this code on Ubuntu 10.04 with Python 2.6.5. >>> Why do the functions g and gggg behave differently? If calls gggg(3) and >>> g(3) both exit their functions in the same state, why do they not enter >>> in >>> the same state when I call gggg(4) and g(4)? >>> >>> # ---------------------------------------------------------------------- >>> my >>> code: >>> def gggg(a, L=[]): >>> >> >> This is a common newbie stumbling-block: Don't use lists (or anything >> mutable) as default argument values >> > > That really should be an error. Pylint warns about it. I think that's enough. I think it's enough, in part because unfortunately default values have become overloaded as the way of creating variables with a global lifetime, and sometimes that's useful to have. I think it would probably have been better to make default arguments be evaluated once per function/method invocation, and add a static modifier to variables, but oh well.
-- http://mail.python.org/mailman/listinfo/python-list
