gistfile1.py

class Ebook():
    def set_author(self, element):
        self.author = element.text

    def set_pubdate(self, element):
        self.pubdate = element.text

    lookup_table = {
        'pg:author ...': self.set_author,
        'pg:pubdate ...': self.set_pub_date
        }

def parse_ebook(etree_book):
    new_book = Ebook()
    for child in etree_book.getchildren():
        # get the signiture of the element, ie 'pg:author' via child.tag
        tag = child.tag
        # get the function out of the lookup_table that matches 'tag'
        func = new_book.lookup_table[tag]
        # call the function on the child element
        func(child)

        # or all in one line
        new_book.lookup_table[child.tag](element)