On Jan 1, 9:00 am, bukzor <[EMAIL PROTECTED]> wrote: > On Dec 31 2007, 1:30 pm, "Chris Mellon" <[EMAIL PROTECTED]> wrote: > > > > > On Dec 31, 2007 2:08 PM, Odalrick <[EMAIL PROTECTED]> wrote: > > > > On 31 Dec, 18:22, Arnaud Delobelle <[EMAIL PROTECTED]> wrote: > > > > On Dec 31, 10:58 am, Odalrick <[EMAIL PROTECTED]> wrote: > > > > > > On 30 Dec, 17:26, George Sakkis <[EMAIL PROTECTED]> wrote: > > > > > > > On Dec 29, 9:14 pm, bukzor <[EMAIL PROTECTED]> wrote: > > > > > > > > Here's the answer to the > > > > > > > question:http://www.python.org/doc/faq/general/#why-are-default-values-shared-... > > > > > > > > It looks like Guido disagrees with me, so the discussion is > > > > > > > closed. > > > > > > > Note that the FAQ mainly explains *what* happens, not *why* was this > > > > > > decision taken. Although it shows an example where "this feature can > > > > > > be useful", it's neither the only way to do it nor is memoization as > > > > > > common as wanting fresh default arguments on every call. > > > > > > I'm surprised noone has said anything about the why of default > > > > > mutables. I think it is becasue it isn't easy to do it an other way. > > > > > [...] > > > > > There is an easy enough way: evaluate default values when the function > > > > is called rather than when it is defined. This behaviour comes with > > > > its own caveats as well I imagine, and it's not 'as easy' to implement > > > > as the current one. > > > > Adding overhead to *all* function calls, even the ones without mutable > > > defaults. That doesn't sound like an attractive tradeoff. > > > And also removing the only way you can currently do early binding in > > Python. I agree that it's a gotcha, but unless someone comes up with > > an answer to the following questions, I'll stick with the status quo > > (Note that this is not blind Python group-think as a previous poster > > implied, but a pragmatic decision that this is the most practical > > solution): > > > a) If we don't evaluate default arguments at function compilation, > > when do we do it? > > b) If you do it at call time, how do you implement early binding? > > c) If you want to introduce new syntax for the current behavior, what > > is it and can you justify it? > > d) What are the performance implications of your proposal versus the > > current behavior? > > > Note that the desired behavior can be implemented under the current > > behavior, at the expense of verbosity - using factories and sentinel > > values as the default arguments, and then expanding them in the > > function. It's not possible to implement the current behavior of > > early-bound arguments if default arguments are evaluated with every > > call. This alone is a good reason to keep the current behavior until > > someone actually has a good alternative that covers the current use > > cases and isn't just upset by the behavior. > > I'm confused by what you mean by 'early binding'. Can you give a quick- > n-dirty example? > > Thanks, > --Buck
Is an 'early bound' variable synonymous with a 'static' variable (in C)? -- http://mail.python.org/mailman/listinfo/python-list
