I get the same resluts if I make the string by str(123.0).  I was thinking it should test True for the isdecimal case for that.

It seems I missunderstood their purpose/use.  This seems like it would be a very common misunderstanding.

It appears, (Because it isn't stated in the doc strings), that they are for testing what specific sub-group of unicode data, the individual character(s) are in.  I think the methods doc strings should say this and be worded so they are more character specific.  

   """ Tests each character, and returns true if
    all of them are in the unicode _______ sub-group. """

As for testing weather or not a string as a whole represents a number value, it seems try/except is still the best way.  :-/