I would recommend you to use in this case method get_article_url instead of print_version. In get_article_url you have access to the xml and you can override all article entries with print version:
Code:
def get_article_url(self, article):
raw_url = article.get('link', None)
date_url = article.get('pubDate', None)
#Extract values from date_url
#we assume you have the final version of date string in datestr variable
datestr = "<processed valid value>"
art_id = raw_url.rsplit('/article_')[1]
nurl = raw_url.replace('http://www.somewebsite.com/','http://www.somewebsite.com/print/' + datestr + '/' + art_id)
return nurl
With such code you do not need print_version at all
Examples of this you can see at various recipes like La prensa, NIN etc.