Strange error with unbound method

[Jeff Epler]

On Mon, 16 Apr 2001 18:26:17 +0200, Fernando Rodríguez
 <spamers at must.die> wrote:
> TypeError: unbound method must be called with class instance 1st argument

I see you solved your problem, but asked for a more helpful error message.
I suggest that the replacement might function like the following:

    class UnboundInstanceMethod(TypeError):
        def __init__(self, arg):
            if type(arg) == types.InstanceType:
                self.str = "instance of %s" % arg.__class__.__name__
            else:
                self.str = type(arg).__name__

        def __str__(self):
            return ("unbound method must be called with class "
                    "instance 1st argument, not %s" % self.str)

>>> raise UnboundInstanceMethod, 1
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
__main__.UnboundInstanceMethod: unbound method must be called with class instance 1st argument, not int
>>> raise UnboundInstanceMethod, X()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
__main__.UnboundInstanceMethod: unbound method must be called with class instance 1st argument, not instance of X

Of course, this can't be the implementation, since this exception is
raised from C.  But the principle applies.

Maybe 'unbound method of class %s called with %s first argument' is a
better string --- it's somewhat shorter, and it tells you the class the
method exists on too.

Jeff