On Thursday, 16 August 2012 19:49:43 UTC+2, Steven D'Aprano wrote: > On Thu, 16 Aug 2012 10:03:51 -0700, Richard Thomas wrote: > > > > > class Foo(object): > > > def __new__(cls, arg): > > > if isinstance(arg, list): > > > cls = FooList > > > elif isinstance(arg, dict): > > > cls = FooDict > > > return object.__new__(cls, arg) > > > > > > class FooList(Foo, list): > > > pass > > > > > > class FooDict(Foo, dict): > > > pass > > > > > > Did you actually try your code? >
I rarely test code. I'm confident in, however undeserved the confidence. :) In this case that's not an error I've ever seen before. Obvious easy fix: return cls.__new__(cls, arg) Incidentally when I reply to your posts through the groups.google.com interface it inserts a blank quoted line between each pair of lines. My first thought was that it was a line endings bug with Google's app but in retrospect that seems very likely to have been fixed years ago. Any ideas? -- http://mail.python.org/mailman/listinfo/python-list
