On Feb 16, 2:14 pm, Peter Otten <[EMAIL PROTECTED]> wrote: > Johny wrote: > > I have > > string="""<span class="test456">55</span>. > > <td><span class="test123">128</span> > > <span class="test789">170</span> > > """ > > > where I need to replace > > <span class="test456">55</span>. > > <span class="test789">170</span> > > > by space. > > So I tried > > > ############# > > import re > > string="""<td><span class="test456">55</span>.<span > > class="test123">128</span><span class="test789">170</span> > > """ > > Newstring=re.sub(r'<span class="test(?!123)">.*</span>'," ",string) > > ########### > > > But it does NOT work. > > Can anyone explain why? > > "(?!123)" is a negative "lookahead assertion", i. e. it ensures that "test" > is not followed by "123", but /doesn't/ consume any characters. For your > regex to match "test" must be /immediately/ followed by a '"'. > > Regular expressions are too lowlevel to use on HTML directly. Go with > BeautifulSoup instead of trying to fix the above. > > Peter- Hide quoted text - > > - Show quoted text -
Yes, I know "(?!123)" is a negative "lookahead assertion", but do not know excatly why it does not work.I thought that (?!...) Matches if ... doesn't match next. For example, Isaac (?!Asimov) will match 'Isaac ' only if it's not followed by 'Asimov'. -- http://mail.python.org/mailman/listinfo/python-list
