Thanks, Alexandre!  Agreed on both points.  I don't really want to allow u'big' and u'little', but I think that's just my laziness talking.  (Apart from that, I have a working patch.)

There's some precedent for not allowing the unicode versions:

>>> float.__getformat__("double")
'IEEE, little-endian'
>>> float.__getformat__(u"double")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: __getformat__() argument must be string, not unicode

But I admit it isn't particularly compelling.