xmlDictTools.py

# Based on http://code.activestate.com/recipes/577722-xml-to-python-dictionary-and-back/ 
# Create python xml structures compatible with
# http://search.cpan.org/~grantm/XML-Simple-2.18/lib/XML/Simple.pm

from lxml import etree
from itertools import groupby

def xml2d(e):
 """Convert an etree into a dict structure

 @type e: etree.Element
 @param e: the root of the tree
 @return: The dictionary representation of the XML tree
 """
 # Namespace magic 
 defns = ""
 if None in e.nsmap:
 defns = "{{{0}}}".format(e.nsmap[None])
 
 def _xml2d(e): 
 kids = {}
 for key in dict(e.attrib):
 kids["#" + key] = e.attrib[key] 
 for k, g in groupby(e, lambda x: x.tag):
 g = [ _xml2d(x) for x in g ] 
 if len(g) == 1:
 g = g[0]
 if k.startswith(defns):
 kids[k.replace(defns,"")]= g
 else:
 kids[k]= g
 if not kids:
 return e.text.strip()
 return kids

 tag = e.tag
 if tag.startswith(defns):
 tag = tag.replace(defns,"")
 
 return { tag : _xml2d(e), '!namespaces': e.nsmap }


def d2xml(d):
 """convert dict to xml

 1. The top level d must contain a single entry i.e. the root element 
 2. Keys of the dictionary become sublements or attributes
 3. Keys that start with # are attributes
 4. If a value is a simple string, then the key subelement and the value is text.
 5. if a value is dict then, then key is a subelement
 6. if a value is list, then key is a set of sublements

 a = { 'module' : {'tag' : [ { 'name': 'a', 'value': 'b'},
 { 'name': 'c', 'value': 'd'},
 ],
 'gobject' : { 'name': 'g', 'type':'xx' },
 'uri' : 'test',
 }
 }
 >>> d2xml(a)
 <module uri="test">
 <gobject type="xx" name="g"/>
 <tag name="a" value="b"/>
 <tag name="c" value="d"/>
 </module>

 @type d: dict 
 @param d: A dictionary formatted as an XML document
 @return: A etree Root element
 """
 def _d2xml(d, p): 
 for k,v in d.items():
 if k.startswith("#"):
 p.set(k[1:],v) 
 elif isinstance(v,dict):
 node = etree.SubElement(p, k)
 _d2xml(v, node)
 elif isinstance(v,list):
 for item in v:
 node = etree.SubElement(p, k)
 _d2xml(item, node)
 else:
 node = etree.SubElement(p, k)
 node.text = v 

 # Namespace magic
 nsmap = None
 if '!namespaces' in d:
 nsmap = d['!namespaces']
 del d['!namespaces']
 k,v = d.items()[0]
 if nsmap:
 d['!namespaces'] = nsmap
 node = etree.Element(k, nsmap=nsmap)
 _d2xml(v, node)

 return node
 
 

if __name__=="__main__":

 X = """<T uri="boo"><a n="1"/><a n="2"/><b n="3"><c x="y"/></b><d>Test</d></T>"""
 print X
 Y = xml2d(etree.XML(X))
 print Y
 Z = etree.tostring (d2xml(Y) )
 print Z
 assert X == Z