On Wed, 2006-04-19 at 17:17 -0700, Carroll, Barry wrote:
>  Greetings:
>  
>  I am writing a function that accepts a string of decimal digits,
>  calculates a checksum and returns it as a single character string.  
>  The first step in the calculation is to split the input into two
>  strings: the even- and odd- numbered digits, respectively.  The least
>  significant digit is defined as odd.  
>  
This sounds like credit card checksum processing.  This is my code for
that:

def isbad(cardnumber):
    factors = ([2,1] * 8)[-len(cardnumber):]        # alternating factors of 2 and 1 ending 
with 1
    chkprods = [int(d)*f for (d,f) in zip(cardnumber,factors)]
    return sum(chkprods) % 10

This deviates quite a bit from your description and the description of
the algorithm that I was working from.  It was only after I had coded up
separate even/odd character lists and looked at what was going on that I
realized there was a much simpler way to describe the rules.

Hopefully, I am not off in left field here.

>  The following code fragment does the job but seems sort of brutish and inelegant to me:
>  
>  >>>>>>>
>  >>> s = '987654321'
>  >>> odd = ''
>  >>> for c in s[::-2]:
>  ...     odd = c + odd
>  ...     
>  >>> s = s[:-1]
>  >>> even = ''
>  >>> for c in s[::-2]:
>  ...     even = c + even
>  ...     
>  >>> odd
>  '97531'
>  >>> even
>  '8642'
>  >>>>>>>
>  
>  Is there a better (i.e. more Pythonic) way to do this?  
>  
>  Thanks in advance for all your help.
>  
>  Regards,
>   
>  Barry
>  barry.carroll@[...].com
>  541-302-1107
>  ________________________
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>  -Quarry worker's creed
>  
>  
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Venix Corp

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