Question

Problem 4 (DOM operations - 30 points): Consider the Python code snippet bookstore.py for DOM operation, some basic methods and properties and an xml file on bookstore which we discussed this week. Wite two func- tions; First, write a recursive Python function get_text(elm) to extract all the text of a dom tree pointed by elm. For example, get_text(elm), where elm=<bookstore>, will return [[u'Emacs User Manual', u'Richard Stallman', u'1980', u'12.00'], [u'Timeline', u'Michael Chricton', u'1999', u'15.00'], [u'Catch 22', u'Joseph Heller', u'1961', u'20.00'], [u'Lost Symbol', u'Dan Brown', u'2009', u'15.00'], [u'The Hitchhikers Guide to The Galaxy', u'Doug Adams', u'1978', u'10.00']] while get_text(elm), where elm=<book category="comedy" cover="hardcopy">, will return [u'Catch 22', u'Joseph Heller', u'1961', u'20.00'] Second, write another function as described in (b) which uses the function you just wrote in part (a). bookstore.py bookstore.xml import re from xml.dom.minidom import parse, parse String def process_dom_tree(dm): Ist = 0 elms = dm.getElementsByTagName('book') l/print elms.length, elms for elm in elms: I = get_text(elm) Ist.append(1) return ist def main(): Ist = 0 global dom dom = parse("bookstore.xml') Ist = process_dom_tree(dom) return Ist <?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book category="computer"> <title lang="en">Emacs User Manual</title> sauthor>Richard Stallman</author> year>1980</year> <price>12.00</price> </books <book category="scifi" cover="paperback"> <title lang="en">Timeline</title> <author>Michael Chricton</author> syear>1999</year> <price>15.00</price> </books <book category="comedy" cover="hardcopy"> <title lang="en">Catch 22</title> <author Joseph Heller</author> syear>1961</year <price>20.00</price> </book <book category="mystery" cover="paperback"> <title lang="en">Lost Symbol</title> <author>Dan Brown</author> <year>2009</year <price>15.00</price> </book <book category="comedy" cover="hardcopy"> <title lang="en">The Hitchhikers Guide to The Gal- axy</title> <author>Doug Adams</author> syear>1978</year> <price>10.00</price> </book> </bookstore> if main__": _name main() methods and properties elm.node Type -> returns an integer # 3=text and 4=cdata elm.data -> returns a string elm.childNodes -> returns list elm.attributes -> returns list elm.getElementsByTagName(tag) -> returns list elm.getAttribute(atr) -> returns a string elm.hasAttributes() -> returns true (value) or false (None)

Answer 1

Working code implemented in Python and appropriate comments provided for better understanding:

Here I am attaching code for these files:

• bookstore.py
• bookstore.xml

Source code for bookstore.py:

import re
from xml.dom.minidom import parse, parseString

def process_dom_tree(dm):
   lst = []
   elms = dm.getElementsByTagName('book')
   for elm in elms:
       l = get_text(elm)
       lst.append(l)
   return lst

def get_text(elm):
   lst = []
   if elm.nodeType in (3,4):
       if not elm.data.isspace():
           lst.append(elm.data)
   else:
       for child in elm.childNodes:
           lst = lst + get_text(child)
   return lst
  
# Retrieve all the text strings for the books published before 1990.
def get_old_books():
   return list(filter(lambda x: int(x[2]) < 1990, process_dom_tree(dom)))

def main():
   lst = []
   global dom
   dom = parse('bookstore.xml')
   lst = process_dom_tree(dom)
   print(lst)
   print("\nBooks published before 1990:")
   print(get_old_books())
   return lst

if __name__ == "__main__":
   main()

Code Screenshots:

Source code for bookstore.xml:

<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
   <book category="computer">
       <title lang="en">Emacs User Manual</title>
       <author>Richard Stallman</author>
       <year>1980</year>
       <price>12.00</price>
   </book>
   <book category="scifi" cover="paperback">
       <title lang="en">Timeline</title>
       <author>Michael Chricton</author>
       <year>1999</year>
       <price>15.00</price>
   </book>
   <book category="comedy" cover="hardcopy">
       <title lang="en">Catch 22</title>
       <author>Joseph Heller</author>
       <year>1961</year>
       <price>20.00</price>
   </book>
   <book category="mystery" cover="paperback">
       <title lang="en">Lost Symbol</title>
       <author>Dan Brown</author>
       <year>2009</year>
       <price>15.00</price>
   </book>
   <book category="comedy" cover="hardcopy">
       <title lang="en">The Hitchhikers Guide to The Galaxy</title>
       <author>Doug Adams</author>
       <year>1978</year>
       <price>10.00</price>
   </book>
</bookstore>

Sample Output Screenshots:

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