python - How to update XML file with lxml -

I want to update the xml file with the new information using the lxml library. For example, I have this code:

  & gt; & Gt; & Gt; From the Lxml Import Entry & gt; & Gt; & Gt; & Gt; & Gt; & Gt; Tree = etree.parse ('books.xml')   
 Where in the 'books.xml' file, this content is:  
 I have this file with new ones Book I want to update:  
  & gt; & Gt; & Gt; New_entry = etree.fromstring ("book" = book category = "web" cover = "paperback" & gt; ... & lt; title = lang = "en" & gt; Learning XML 2 & lt; / title & Gt; ... & lt; author & gt; Eric Re & lt; / author & gt; ... & lt; year & gt; 2006 & lt; / year & gt; ... & lt; value & Gt; 49.95 & lt; / price & gt; ... & lt; / book & gt; '' ')   
 My question is, I  tree  How can I update the tree with the  new_entry  tree and save the file.   
 
 
 You go here, get root of the tree, add your new element, the tree in the file Save as String:  
  lxml Import Entry Tree = etree.parse ('books.xml') new_entry = etree.fromstring ('' '' book category = "web" cover = "Paperback" & gt; Title lang = "en" & gt; Learning XML 2 & lt; / title & gt; & lt; Author & gt; Eric Re & lt; / Authors & gt; & lt; Year> 2006 & lt; / year & gt;  49.95   '' ') Tree.getroot () Route. Append ( New_entry) f = open ('books-mod.xml', 'w') f.write (etree.tostring (root, pretty_print = T Ru E)) f.close ()