Match First Sequence in Regular Expression?

[Michael Spencer]

Roger L. Cauvin wrote:
> "Fredrik Lundh" <fredrik at pythonware.com> wrote in message 
> news:mailman.1088.1138296051.27775.python-list at python.org...
>> Roger L. Cauvin wrote:
>>
>>>> $ python test.py
>>>> got    expected
>>>> ---------------
>>>> accept accept
>>>> reject reject
>>>> accept accept
>>>> reject reject
>>>> accept accept
>>> Thanks, but the second test case I listed contained a typo.  It should 
>>> have
>>> contained a sequence of three of the letter 'a'.  The test cases should 
>>> be:
>>>
>>> "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

  >>> test(pattern)
  got    expected
  ------ --------
  accept accept
  reject reject
  accept accept
  reject reject
  accept accept
  >>>

  >>> testsuite = (
  ...     ("xyz123aaabbab", "accept"),
  ...     ("xyz123aabbaaab", "reject"),
  ...     ("xayz123aaabab", "accept"),
  ...     ("xaaayz123abab", "reject"),
  ...     ("xaaayz123aaabab", "accept"),
  ...     )
  >>>
  >>> def test(pattern):
  ...     print "got    expected"
  ...     print "------ --------"
  ...     for string, result in testsuite:
  ...         m = re.match(pattern, string)
  ...         if m:
  ...             print "accept",
  ...         else:
  ...             print "reject",
  ...         print result
  ...
  >>>

Michael