[Iceybones]

I think I've narrowed it down to this block of code. Thoughts?

goodreads_edition_book['goodreads_isbn'] = ''
            isbn_node = edition_data_node.xpath('div[@class="moreDetails hideDetails"]/div[@class="dataRow"][2]/div[@class="dataValue"]/span[@class="greyText"]/text()')
            if len(isbn_node) > 0:
                isbn = None
                match_isbn = re.search(': (\d+)', isbn_node[0])
                if not match_isbn:
                    match_isbn = re.search('(\d+)', isbn_node[0])
                if match_isbn:
                    isbn = match_isbn.groups(0)[0]
                    if check_isbn(isbn):
                        goodreads_edition_book['goodreads_isbn'] = isbn
            goodreads_edition_books.append(goodreads_edition_book)