excluding search string in regular expressions

[Bengt Richter]

On Thu, 21 Oct 2004 13:36:46 +0200, Franz Steinhaeusler <franz.steinhaeusler at utanet.at> wrote:

>Hello,
>
>Following Problem:
>
>find only occurances, where in the line are'::' characters and
>the former line is not equal '**/'
>
>so 2) and 3) should be found and 1) not.
>
>1)
>"""
>**/
>void C::B
>"""
>
>2)
>"""
>
>void C::B
>"""
>
>3)
>"""
>*/
>void C::B
>"""
>
>I tried something
>"\*\*/\n.*::"
>
>But this is the opposite.
>
>So my question is: how can I exclude a pattern?
>
>single characters with [^ab] but I need not(ab)
>
>not_this_brace_pattern(\*\*/\n).*::
>
>thank you in advance,

To look back a line, I think I'd just use a generator, and test current
and last lines to get what I wanted. E.g., perhaps you can adapt this:
(I am just going literally by
 """
 find only occurances, where in the line are'::' characters and
 the former line is not equal '**/'
 """
which doesn't need a regex)

 >>> def findem(lineseq):
 ...    getline = iter(lineseq).next
 ...    curr = getline().rstrip()
 ...    while True:
 ...        last, curr = curr, getline().rstrip()
 ...        if '::' in curr and last != '**/': yield curr
 ...

I made a file, modifying your data a little:

 >>> print '----\n%s----'% file('franz.txt').read()
 ----
 1)
 """
 **/
 void C::B -- no (1)
 """

 2)
 """

 void C::B -- yes (2)
 """

 3)
 """
 */
 void C::B -- yes (3)
 """
 ----

Here's what the generator returns:

 >>> for line in findem(file('franz.txt')): print repr(line)
 ...
 'void C::B -- yes (2)'
 'void C::B -- yes (3)'


Regards,
Bengt Richter