json2xml python script

#!/usr/bin/python

import sys
import json
import traceback
import getopt
import numbers

from xml.dom.minidom import Document

def parse_element(doc, root, j):
if isinstance(j, dict):
for key in j.keys():
value = j[key]
if isinstance(value, list):
for e in value:
elem = doc.createElement(key)
parse_element(doc, elem, e)
root.appendChild(elem)
else:
if key.isdigit():
elem = doc.createElement('item')
elem.setAttribute('value', key)
else:
elem = doc.createElement(key)
parse_element(doc, elem, value)
root.appendChild(elem)
elif isinstance(j, str) or isinstance(j, unicode):
text = doc.createTextNode(j)
root.appendChild(text)
elif isinstance(j, numbers.Number):
text = doc.createTextNode(str(j))
root.appendChild(text)
else:
raise Exception("bad type '%s' for '%s'" % (type(j), j,))

def parse_doc(root, j):
doc = Document()
if root is None:
if len(j.keys()) > 1:
raise Exception('Expected one root element, or use --root to set root')
root = j.keys()[0]
elem = doc.createElement(root)
j = j[root]
else:
elem = doc.createElement(root)
parse_element(doc, elem, j)
doc.appendChild(elem)
return doc

def parse_json_example():
js = r"""{"object": {"content": "bla bla bla", "type": "note", "links": {"alternate": [{"href": "http://www.google.com/buzz/111/222", "type": "text/html"}, {"href": "http://www.google.com/buzz/1111/2222", "type": "text/html"}]}}, "id": "tag:google.com,2010:buzz:1111", "links": {"alternate": [{"href": "http://www.google.com/buzz/11111/222", "type": "text/html"}]}}"""
j = json.loads(js)
doc = parse_doc("post", j)
print doc.toprettyxml(encoding="utf-8", indent="  ")

def parse_json_stdin(root):
js = "".join(sys.stdin.readlines())
j = json.loads(js)
doc = parse_doc(root, j)
print doc.toprettyxml(encoding="utf-8", indent="  ")

def usage():
print '''
Usage:    %s <-r root element>

-r (--root):        root element name

Exiting...
''' % (sys.argv[0])

def main():

root = None

if len(sys.argv[1:]):
try:
(opts, args) = getopt.getopt(sys.argv[1:], 'r:', ['root'])
if (len(args)):
raise getopt.GetoptError('bad parameter')
except getopt.GetoptError:
usage()
sys.exit(0)

for (opt, arg) in opts:
if opt in ('-r', '--root'):
root = arg

parse_json_stdin(root)

if __name__ == '__main__':
try:
main()
except:
print >> sys.stderr, '\nException!!!'
print >> sys.stderr, '-' * 50
traceback.print_exc()
print >> sys.stderr, '-' * 50