If you don't have such a package, you can try:

def json2xml(json_obj, line_padding=""):
    result_list = list()

    json_obj_type = type(json_obj)

    if json_obj_type is list:
        for sub_elem in json_obj:
            result_list.append(json2xml(sub_elem, line_padding))

        return "\n".join(result_list)

    if json_obj_type is dict:
        for tag_name in json_obj:
            sub_obj = json_obj[tag_name]
            result_list.append("%s<%s>" % (line_padding, tag_name))
            result_list.append(json2xml(sub_obj, "\t" + line_padding))
            result_list.append("%s</%s>" % (line_padding, tag_name))

        return "\n".join(result_list)

    return "%s%s" % (line_padding, json_obj)

For example:

s='{"main" : {"aaa" : "10", "bbb" : [1,2,3]}}'
j = json.loads(s)
print(json2xml(j))

Result:

<main>
        <aaa>
                10
        </aaa>
        <bbb>
                1
                2
                3
        </bbb>
</main>

There is no "one-to-one" mapping between XML and JSON, so converting one to the other necessarily requires some understanding of what you want to do with the results.

That being said, Python's standard library has several modules for parsing XML (including DOM, SAX, and ElementTree). As of Python 2.6, support for converting Python data structures to and from JSON is included in the json module.

So the infrastructure is there.