Greetings:

First of all, thanks to those who contributed suggestions.  

Unfortunately, my description was incomplete.
 
>  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.
 
I forgot to include two important requirements:

    1. the length of the input string is arbitrary,
    2. the order of the digits must be maintained.

I could not find a way to include these requirements in a single, simple
expression.  I decided to make an explicit test for string length, which
simplified matters. I came up with this:

> >>>>>>
> >> def odd_even(x):
...     if len(x) % 2 == 1:
...         return x[::2], x[1::2]
...     else:
...         return x[1::2], x[::2]

> >> odd_even('987654321')
('97531', '8642')

> >> odd_even('98765432')
('8642', '9753')
> >> 
> >>>>>>

which is an improvement, I think, on my original.  
 
>  >>>>>>>
>  >>> 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'
>  >>>>>>>
 
Thanks again.  This is the most useful list I've ever found.

Regards,
 
Barry
barry.carroll@[...].com
541-302-1107
________________________
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-Quarry worker's creed


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