> Can we do better?  How about a new field on the Parameter object, "symbolic_default_value", which shows you the expression used to compute the value?  We could then set default_value to the result of the expression, pydoc could print the symbolic expression, and codecs encode/decode could be more straightforward.

Maybe it's a good idea, but I'm -1 on pushing new APIs to 3.5 without some careful consideration at this super late stage (and it's not going to be a small change btw).

Let's just fix the codecs module.