how to get specific nodes in xml file with python

Assuming your document is called assets.xml and has the following structure:

<assets>
    <AssetType>
        ...
    </AssetType>
    <AssetType>
        ...
    </AssetType>
</assets>

Then you can do the following:

from xml.etree.ElementTree import ElementTree
tree = ElementTree()
root = tree.parse("assets.xml")
for assetType in root.findall("//AssetType[@longname='characters']"):
    for type in assetType.getchildren():
        print type.text

If you don't mind loading the whole document into memory:

from lxml import etree
data = etree.parse(fname)
result = [node.text.strip() 
    for node in data.xpath("//AssetType[@longname='characters']/type")]

You may need to remove the spaces at the beginning of your tags to make this work.

You could use the pulldom API to handle parsing a large file, without loading it all into memory at once. This provides a more convenient interface than using SAX with only a slight loss of performance.

It basically lets you stream the xml file until you find the bit you are interested in, then start using regular DOM operations after that.

from xml.dom import pulldom

# http://mail.python.org/pipermail/xml-sig/2005-March/011022.html
def getInnerText(oNode):
    rc = ""
    nodelist = oNode.childNodes
    for node in nodelist:
        if node.nodeType == node.TEXT_NODE:
            rc = rc + node.data
        elif node.nodeType==node.ELEMENT_NODE:
            rc = rc + getInnerText(node)   # recursive !!!
        elif node.nodeType==node.CDATA_SECTION_NODE:
            rc = rc + node.data
        else:
            # node.nodeType: PROCESSING_INSTRUCTION_NODE, COMMENT_NODE, DOCUMENT_NODE, NOTATION_NODE and so on
           pass
    return rc


# xml_file is either a filename or a file
stream = pulldom.parse(xml_file) 
for event, node in stream:
    if event == "START_ELEMENT" and node.nodeName == "AssetType":
        if node.getAttribute("longname") == "characters":
            stream.expandNode(node) # node now contains a mini-dom tree
            type_nodes = node.getElementsByTagName('type')
            for type_node in type_nodes:
                # type_text will have the value of what's inside the type text
                type_text = getInnerText(type_node)