Match First Sequence in Regular Expression?

[Roger L. Cauvin]

"Michael Spencer" <mahs at telcopartners.com> wrote in message 
news:mailman.1096.1138299292.27775.python-list at python.org...
> Roger L. Cauvin wrote:
>
>>>> "xyz123aaabbab" accept
>>>> "xyz123aabbaaab" reject
>>>> "xayz123aaabab" accept
>>>> "xaaayz123abab" reject
>>>> "xaaayz123aaabab" accept
>>>>
> This passes your tests.  I haven't closely followed the thread for other 
> requirements:
>
>  >>> pattern = ".*?(?<![a+b])aaab" #look for aaab not preceded by any a+b

Very interesting.  I think you may have solved the problem.  The key seems 
to be the "not preceded by" part.  I'm unfamiliar with some of the notation. 
Can you explain what "[a+b]" and the "(?<!" do?

-- 
Roger L. Cauvin
nospam_roger at cauvin.org (omit the "nospam_" part)
Cauvin, Inc.
Product Management / Market Research
http://www.cauvin-inc.com