I'm new to Python, so there may be a better way to do this. However, this is how I would do it:
Code:
parts = re.match(r"(?P<begin>http://www.elnuevoherald.com/\d+/\d+/\d+)(?P<end>/\d+/.+\.html)", feed)
feed = parts.group('begin') + "/v-print" + parts.group('end')