xml.dom.minidom nodeValue returns none

[iamfletch]

What causes nodeValue to be None?
Im trying to connect to facebook, my lack xml experiance with python is letting me down. Can anyone explain the following?

def getReply(self, params):
  req = urllib.urlopen(facebook.getURL(params))
  tokenXML = req.read()
  req.close()
  print 'Raw data: ', tokenXML
  return tokenXML
 
tokenXML = parseString(facebook.getReply(params))
token = tokenXML.getElementsByTagName('auth_createToken_response')[0]
print 'toString: ', token
print 'nodeValue: ', token.nodeValue
 

Gives the following:

C:\Users\simon\Documents\Flash\air\fb++\server>server.py
Raw data:  <?xml version="1.0" encoding="UTF-8"?>
<auth_createToken_response xmlns="http://api.facebook.com/1.0/" xmlns:
xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="ht
tp://api.facebook.com/1.0/ http://api.facebook.com/1.0/facebook.xsd">9
ea0d6592e0f761255e549fbd180443a</auth_createToken_response>
 
toString:  <DOM Element: auth_createToken_response at 0x2335328>
nodeValue:  None
 

[bvdet]

parseString method getElementsByTagName returns a list. The string held between the open and closing tags is a child node that is accessed with element method childNodes. You would access the text between the tags similar to this:

from xml.dom.minidom import parse, parseString
 
xmlStr = '''<?xml version="1.0" encoding="UTF-8"?>
<auth_createToken_response
 xmlns="http://api.facebook.com/1.0/"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://api.facebook.com/1.0/facebook.xsd">
 9ea0d6592e0f761255e549fbd180443a
</auth_createToken_response>'''
 
xmlDoc = parseString(xmlStr)
for elem in xmlDoc.getElementsByTagName('auth_createToken_response'):
    for child in elem.childNodes:
        print repr(child.nodeValue.strip())

I formatted the XML string for readability.

[bvdet]

You can also get the desired result in this case using method firstChild which returns the first child element or None:

xmlDoc = parseString(xmlStr)
for elem in xmlDoc.getElementsByTagName('auth_createToken_response'):
    child = elem.firstChild
    if child:
        print repr(child.nodeValue.strip())

[iamfletch]

thanks, is it me or does it make no sense to find it by tagname then have to access it by using childNodes/firstChild.

Thanks for the fast response.
simon

[bvdet]

A tag can encompass any number of nested elements of different types. A text element (node.nodeType == 3) is just one type of node. When you look at it this way, it makes some sense. Take a look at this XML DOM tutorial.

[iamfletch]

I get ya, makes sense sort of.