[Python-3000] Types and classes

[Guido van Rossum]

On Tue, Apr 8, 2008 at 5:34 PM, Greg Ewing <greg.ewing at canterbury.ac.nz> wrote:
> Guido van Rossum wrote:
>
>  > Seems to be mass confusion all around. My proposal is:
>  >
>  > repr(int) == <class 'int'>
>  > str(int) == 'int'
>  >
>
> > repr(C) == <class '__main__.C'>
>  > str(c) == '__main__.C'
>
>  Can I take a step back and ask why exactly we're considering
>  doing this? In what use cases is the current result
>  of str() considered too verbose?

In error messages. I've written more code than I'd like to admit that
spits out errors of the form "Method frumble() expected a joojoo or
geegee argument, but got a %s instead". Using type(arg).__name__ omits
the module name, which can be ambiguous in some contexts (some apps
have lots of different but related classes with the same name defined
in different modules). Using repr(type(arg)) makes the message ugly
(and longer, which matter). Making it pretty requires something like
type(arg).__module__ + "." + type(arg).__name__ with an exception if
__module__ is empty or '__builtin__' is usually not worth the code. A
simpler str() for classes would simplify life.

And don't tell me that I shouldn't be using isinstance().

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)