How to add a class to a hyperlink when it contains a specific file extension?

Can someone tell me how to take a string and run a function against it to check for a specific type of file (say 开发者_如何学Goa ".pdf"). If the string contains the file, then it needs to apply a "pdf" class to the anchor that contains the link.

Here's an example of a string:

<a href="/downloads/myfile.pdf">My PDF</a>

I would like it to be changed to this:

<a href="/downloads/myfile.pdf" class="pdf">My PDF</a>

---

Do this in CSS:

a[href$=".pdf"] {
   /* some rules */
}

But this may not be supported by some browser.

Alternatively, do this in Javascript, with jQuery or any library:

$('a[href$=".pdf"]').addClass('pdf'); // in jQuery

Or without library:

var elems = document.getElementByTagName('a');
for (var i = 0; i  < elems.length; ++i) {
    var a = elems[i];
    if (/\.pdf$/.test(a.href)) {
        a.className = 'pdf';
    }
}

---

(<a\s+href="[^"]*\.([A-Za-z0-9]{2,5})\s*")([^>]*>) replace by \1 class="\2" \3

python code:

import re,sys
file = sys.argv[1]
f = open(file, 'r')
text = f.read()
f.close()
text = re.sub(r'(<a\s+href="[^"]*\.([A-Za-z0-9]{2,5})\s*")([^>]*>)', r'\1 class="\2" \3', te$
f = open(file+'.re','w')
f.write(text)
f.close()

Can use it to modify html static