Worthwhile to reverse a dictionary

[Larry Bates]

rudysanford at hotmail.com wrote:
> I just started messing with programming and started with Python.  Part
> of my first project deals with translating numerical values to letters.
> I would like to be able to do the reverse as well, letters to numbers,
> sort of a table for lookup and a table for reverse lookup.  I thought
> that a dictionary would be the structure to use- write it once and in a
> second instance swap the keys for values and values for keys.  However,
> reversing a dictionary does not seem to be easily achieved.  Am I using
> the wrong data structure?
> 
This doesn't really answer your question (others have already done this),
but back in the 'ol days we did this:

>>> letters=['a','b','c']
>>> map(lambda x: ord(x)-64, letters)
[1, 2, 3]

This takes advantage of the fact that letters must be stored as
binary integers in ASCII (e.g. 'a' = 65, 'b'=66, etc.).  You can
go the other direction with chr(x).  Not completely sure about
what you want to accomplish, but this eliminates the need for
the dictionaries.

Larry Bates