Negative regular expressions (searching for "i" not inside command)

[castironpi]

On Aug 28, 4:04 pm, "Guilherme Polo" <ggp... at gmail.com> wrote:
> On Thu, Aug 28, 2008 at 5:04 PM, Bart Kastermans
>
> <kaste... at math.wisc.edu${hostname}> wrote:
> > I have a file in which I am searching for the letter "i" (actually
> > a bit more general than that, arbitrary regular expressions could
> > occur) as long as it does not occur inside an expression that matches
> > \\.+?\b (something started by a backslash and including the word that
> > follows).
>
> > More concrete example, I have the string "\sin(i)" and I want to match
> > the argument, but not the i in \sin.
>
> > Can this be achieved by combining the regular expressions?  I do not
> > know the right terminology involved, therefore my searching on the
> > Internet has not led to any results.
>
> Try searching again with the "lookahead" term, or "negative lookahead".
>
>
>
> > I can achieve something like this by searching for all i and then
> > throwing away those i that are inside such expressions.  I am now just
> > wondering if these two steps can be combined into one.
>
> > Best,
> > Bart
> > --
> >http://www.bartk.nl/
> > --
> >http://mail.python.org/mailman/listinfo/python-list
>
> --
> -- Guilherme H. Polo Goncalves

No dice: "This is called a positive lookbehind assertion.  ...The
contained pattern must only match strings of some fixed length."
'finditer' could make the 'combined into one' option more attractive
though.