Can I add methods to built in types with classes?

[CC]

Hi:

I've gotten through most of the "9. Classes" section of the tutorial.  I 
can deal with the syntax.  I understand the gist of what it does enough 
that I can play with it.  But am still a long way from seeing how I can 
use this OOP stuff.

But I have one idea.  Not that the functional approach isn't workable, 
but I have a situation where I need to test if all the characters in a 
string are in the set of hexadecimal digits.

So I wrote:
------------------------------------------
from string import hexdigits

def ishex(word):
     for d in word:
         if d not in hexdigits: return(False)
     else return(True)
------------------------------------------

Then I can do this to check if a string is safe to pass to the int() 
function without raising an exception:

if ishex(string):
     value = int(string, 16)

But can I create a class which inherits the attributes of the string 
class, then add a method to it called ishex()?  Then I can do:

if string.ishex():
     value = int(string, 16)

The thing is, it doesn't appear that I can get my hands on the base 
class definition/name for the string type to be able to do:

---------------------------------------
class EnhancedString(BaseStringType):
     def ishex(self):
         for d in word:
             if d not in hexdigits: return(False)
         else return(True)
---------------------------------------

Thanks.



-- 
_____________________
Christopher R. Carlen
crobc at bogus-remove-me.sbcglobal.net
SuSE 9.1 Linux 2.6.5