您如何遍历使用Python的elmenttree模块解析的Element树？

Question

So I spent about half the day yesterday playing around in the interactive python command line trying to figure out how to navigate this ElementTree, and it's confusing the crap out of me. As per this site https://docs.python.org/2/library/xml.etree.elementtree.html#module-xml.etree.ElementTree I loaded the tree by doing

import xml.etree.ElementTree as ET
tree = ET.parse('nmaptest.xml')
root = tree.getroot()

And then I was going through the examples, and trying to figure out how to access and iterate through each element. Just as soon as I think I'm starting to get how it's pieced together, I can't get it to do what I want it to.

Ultimately I'd like to parse it and dump the pertinent data into a database for later comparison (or maybe write a script that will simply compare two xml docs, but that's looking beyond my abilities currently.)

I've tried things like the following

for host in root.iter('host'):
    print host.attrib['name']
    for address in host.iter('address'):
            print address.attrib['addr']
            for port in host.iter('port'):
                    print port.attrib['portid']

In an attempt to print out the hostname, IP address, and ports open for each... It doesn't quite work, it's almost like hostname and address are in completely different worlds, though I can't see why that would be. I also found out that you can access the address by simply doing

print host[1].attrib['addr']

But I can't find any kind of consistency in when things are indexed by an integer, such as above (since host[3] doesn't appear to be hostname like you'd think it would be, logically, and host[2] seems to be hostnames, but has no .attrib or anything), when they're an attribute, and when they're also a dictionary key. It seems like sometimes when I THINK I've found what I'm looking for, instead of seeing something like

for host in root.iter('host'):
    print host[1].attrib

{'addrtype': 'ipv4', 'addr': '10.1.102.255'}

I'll do a .attrib on something and see empty brackets {} like when I do

for host in root.iter('host'):
    print host[2].attrib

So I'm not understanding how it parses the document at all... I don't suppose anyone can help clear it up or point me to some documentation that might help me?

Here's a sample entry from the XML output...

<host starttime="1408488852" endtime="1408499159"><status state="up" reason="user-set" reason_ttl="0"/>
  <address addr="X.X.X.X" addrtype="ipv4"/>
  <hostnames>
      <hostname name="computername.domainname.com" type="PTR"/>
  </hostnames>
  <ports>
    <extraports state="filtered" count="986">
      <extrareasons reason="no-responses" count="986"/>
    </extraports>
    <port protocol="tcp" portid="X"><state state="open" reason="syn-ack" reason_ttl="127"/>    <service name="X" method="table" conf="3"/></port>
    <port protocol="tcp" portid="X"><state state="open" reason="syn-ack" reason_ttl="127"/>    <service name="X" method="table" conf="3"/></port>
    <port protocol="tcp" portid="X"><state state="open" reason="syn-ack" reason_ttl="127"/>    <service name="X" method="table" conf="3"/></port>
  </ports>
  <times srtt="332" rttvar="164" to="100000"/>
</host>    

Answer 1

With this code,

for host in root.iter('host'):
    print host.attrib['name']

you are trying to access the name attribute of the host element. But it is the hostname element that has that attribute.

Here is one way to get the data that you wanted to extract (assuming that there is one or more host elements as children of a common root element in nmaptest.xml):

import xml.etree.ElementTree as ET
tree = ET.parse('nmaptest.xml')

hosts = tree.findall(".//host")

for host in hosts:
    for elem in host.iter():
        if elem.tag == "hostname":
            print elem.attrib['name']
        if elem.tag == "address":
            print elem.attrib['addr']
        if elem.tag == "port":
            print elem.attrib['portid']

Output:

X.X.X.X
computername.domainname.com
X
X
X