Adding anchors to h2 in text using python and regexp

Question

I'm trying to add anchors to all h2's in my html, using python. This code will add those anchors, but I need to fill the name of the anchors too.

Any idea if the name can be the number of the match in the loop or a slugified version of the text between the h2 tags?

Here's the code so far:

regex = '(?P<name><h2>.*?</h2>)'
text = re.sub(regex, "<a name=''/>"+r"\g<name>", text)

Answer 1

Not sure if I understand correctly, but is placing the author as the name attribute sufficient? Maybe you could use (as long as the author name doesn't contain invalid chars for an attribute):

regex = '(?P<name><h2>(.*?)</h2>)'
print re.sub(regex, "<a name='\g<2>'/>"+r"\g<name>", text)

If you need a more advanced substitution method, parsing the author name or looking up some sort of related id, you could define a replacement function (see re substitute doc):

def name_substitution(matchobj):
    name = matchobj.group(2)
    # do some processing on name here ...
    name = name.replace(' ', '_')
    return "<a name='%s'>%s</a>" % (name, matchobj.group(0))

print re.sub(regex, substitution, text)

Answer 2

You can take advantage of the fact that the second argument to re.sub can be a function to do pretty much anything you'd like. Here's an example that will slugify the text inside the <h2> element:

regex = '(?P<name><h2>(.*?)</h2>)' # Note the extra group inside the <h2>

def slugify(s):
    return s.replace(' ', '-') # bare-bones slugify

def anchorize(matchobj):
    return '<a name="%s"/>%s' % (slugify(matchob.group(2)), matchobj.group(1))

text = re.sub(regex, anchorize, text)

(That slugify function could obviously use some work.)

You could also implement a counter with a version of anchorize that used a global counter or, better yet, a class that kept track of its own counter and implemented the special __call__ method.