iterating in reverse

[Nick Vargish]

I just encountered a problem that required reverse iterating to solve,
and my current solution, though it works, is not so satisfying:

def commafy(val):
    """Return val as string with commas every thousandth place."""
    val = str(val)
    ret = ''
    c = 0
    for i in range(len(val) - 1, -1, -1):
        if c and not c % 3:
            ret = ',' + ret
        ret = val[i] + ret
        c += 1
    return ret

This is one of the few times I just haven't been able to come up with
an elegant and -- dare I say it -- aesthetically pleasing solution in
Python. I suspect the lack is my own, not Python's.

Nick

-- 
# sigmask.py  ||  version 0.2  ||  2003-01-07  ||  Feed this to your Python.
print reduce(lambda x,y:x+chr(ord(y)-1),'Ojdl!Wbshjti!=obwAqbusjpu/ofu?','')