Varable parsing error with python

[OmPs]

In an XML file which contain a tag and then these tags contain properties,
which later are being called in anoter tag where these properties are
expanded as variables.

For eg.







    <instance name='instancename' user='test' group='test'
fullname='test%20-%20dev%20app' >

          <property>

             <APPVERSION>1.0</APPVERSION>

          </property>

    </instance>



    <component name='testappComp' user='test' group='test'>

         <version>1.2</version>

          <os>Red Hat Enterprise Linux Server 5 X86_64</os>

          <package>testsapppath</package>

    </component>





    <package name='testapppath'>

         <description>my testapp area</description>

         <version>${APPVERSION}</version>

    </package>



So now i have written a python program whcih is parsing this program, so
what i am doing in here is reading this xml file



    with open(filename, "r") as f:

    orig_xml = f.read()

    #unescape html characters like %20

    xmlstring = urllib.unquote(orig_xml)

    #convert xml to dict

    doc = xmltodict.parse(xmlstring)

    #replace property values in xml string via instancename

    s = Template(xmlstring)

    #iterate over instances/ match the one we need

    for i in doc.get("application").get("instance", None):

        #when found

        # s/r properties in xml and then convert it back to dict

        try:

            if i.get("@name", None) == instancename:

                try:

                    instance_property = dict(i.get("property"))

                    final_string = s.safe_substitute(instance_property)

                    final_dict = xmltodict.parse(final_string)

                except TypeError:

                    final_dict = doc

        # Handle strings in case of dict, strings do not have get method.

        except AttributeError:

            final_dict = doc



and when i am trying to get the version no. using a function for getting
the package version



    def _getPackgeVersion(xmlfile, p):

        package = str(p)

        if isinstance(fpmdict["application"]["package"], list):

            for i in fpmdict["application"]["package"]:

                if i["@name"] == p:

                    _pkgVersion = i["version"]

        else:

            _pkgversion = fpmdict["application"]["package"]["version"]

            return _pkgVersion



    pkgVersion = _getPackgeVersion(final_doc, testpackage)

    print type(pkgVersion)



I am getting the below error

<type 'NoneType'>
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