I need to parse a soap response and convert to a text file. I am trying to parse the values as detailed below. I am using ElementTree in python
I have the below xml response which I need to parse
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/" xmlns:tmf854="tmf854.v1" xmlns:alu="alu.v1">
<soapenv:Header>
<tmf854:header>
<tmf854:activityName>query</tmf854:activityName>
<tmf854:msgName>queryResponse</tmf854:msgName>
<tmf854:msgType>RESPONSE</tmf854:msgType>
<tmf854:senderURI>https:/destinationhost:8443/tmf854/services</tmf854:senderURI>
<tmf854:destinationURI>https://localhost:8443</tmf854:destinationURI>
<tmf854:activityStatus>SUCCESS</tmf854:activityStatus>
<tmf854:correlationId>1</tmf854:correlationId>
<tmf854:communicationPattern>MultipleBatchResponse</tmf854:communicationPattern>
<tmf854:communicationStyle>RPC</tmf854:communicationStyle>
<tmf854:requestedBatchSize>1500</tmf854:requestedBatchSize>
<tmf854:batchSequenceNumber>1</tmf854:batchSequenceNumber>
<tmf854:batchSequenceEndOfReply>true</tmf854:batchSequenceEndOfReply>
<tmf854:iteratorReferenceURI>http://9195985371165397084</tmf854:iteratorReferenceURI>
<tmf854:timestamp>20220915222121.472+0530</tmf854:timestamp>
</tmf854:header>
</soapenv:Header>
<soapenv:Body>
<queryResponse xmlns="alu.v1">
<queryObjectData>
<queryObject>
<name>
<tmf854:mdNm>AMS</tmf854:mdNm>
<tmf854:meNm>CHEERLAVANCHA_281743</tmf854:meNm>
<tmf854:ptpNm>/type=NE/CHEERLAVANCHA_281743</tmf854:ptpNm>
</name>
<vendorExtensions>
<package>
<NameAndStringValue>
<tmf854:name>hubSubtendedStatus</tmf854:name>
<tmf854:value>NONE</tmf854:value>
</NameAndStringValue>
<NameAndStringValue>
<tmf854:name>productAndRelease</tmf854:name>
<tmf854:value>DF.6.1</tmf854:value>
</NameAndStringValue>
<NameAndStringValue>
<tmf854:name>adminUserName</tmf854:name>
<tmf854:value>isadmin</tmf854:value>
</NameAndStringValue>
<NameAndStringValue>
</package>
</vendorExtensions>
</queryObject>
</queryObjectData>
</queryResponse>
</soapenv:Body>
</soapenv:Envelope>
I need to use the below code snippet.
parser = ElementTree.parse("response.txt")
root = parser.getroot()
inventoryObjectData = root.find(".//{alu.v1}queryObjectData")
for inventoryObject in inventoryObjectData:
for device in inventoryObject:
if (device.tag.split("}")[1]) == "me":
vendorExtensionsNames = []
vendorExtensionsValues = []
if device.find(".//{tmf854.v1}mdNm") is not None:
mdnm = device.find(".//{tmf854.v1}mdNm").text
if device.find(".//{tmf854.v1}meNm") is not None:
menm = device.find(".//{tmf854.v1}meNm").text
if device.find(".//{tmf854.v1}userLabel") is not None:
userlabel = device.find(".//{tmf854.v1}userLabel").text
if device.find(".//{tmf854.v1}resourceState") is not None:
resourcestate = device.find(".//{tmf854.v1}resourceState").text
if device.find(".//{tmf854.v1}location") is not None:
location = device.find(".//{tmf854.v1}location").text
if device.find(".//{tmf854.v1}manufacturer") is not None:
manufacturer = device.find(".//{tmf854.v1}manufacturer").text
if device.find(".//{tmf854.v1}productName") is not None:
productname = device.find(".//{tmf854.v1}productName").text
if device.find(".//{tmf854.v1}version") is not None:
version = device.find(".//{tmf854.v1}version").text
vendorExtensions = device.find("vendorExtensions")
vendorExtensionsNamesElements = vendorExtensions.findall(".//{tmf854.v1}name")
for i in vendorExtensionsNamesElements:
vendorExtensionsNames.append(i.text.strip())
vendorExtensionsValuesElements = vendorExtensions.findall(".//{tmf854.v1}value")
for i in vendorExtensionsValuesElements:
vendorExtensionsValues.append(str(i.text or "").strip())
alu = ""
for i in vendorExtensions:
if i.attrib:
if alu == "":
alu = i.attrib.get("{alu.v1}name")
else:
alu = alu + "|" + i.attrib.get("{alu.v1}name")
The issue is that The below code is not able to find the 'vendorExtensions"'. Please help here.
vendorExtensions = device.find("vendorExtensions")
Have tried the below as well
vendorExtensions = device.find(".//queryObject/vendorExtensions")
Your document declares a default namespace of alu.v1:
<queryResponse xmlns="alu.v1">
...
</queryResponse>
Any attribute without an explicit namespace is in the alu.v1 namespace. You need to qualify your attribute name appropriately:
vendorExtensions = device.find("{alu.v1}vendorExtensions")
While the above is a real problem with your code that needs to be corrected (the Wikipedia entry on XML namespaces may be useful reading if you're unfamiliar with how namespaces work), there are also some logic problems with your code.
Let's drop the big list of conditionals from the code and see if it's actually doing what we think it's doing. If we run this:
from xml.etree import ElementTree
parser = ElementTree.parse("data.xml")
root = parser.getroot()
queryObjectData = root.find(".//{alu.v1}queryObjectData")
for queryObject in queryObjectData:
for device in queryObject:
print(device.tag)
Then using your sample data (once it has been corrected to be syntactically valid), we see as output:
{alu.v1}name
{alu.v1}vendorExtensions
Your search for the {alu.v1}vendorExtensions element will never succeed before the thing on which you're trying to search (the device variable) is the thing you're trying to find.
Additionally, the conditional in your loop...
if (device.tag.split("}")[1]) == "me":
...will never match (there is no element in the entire document for which tag.split("}")[1] == "me" is True).
I'm not entirely clear what you're trying to do, but here's are some thoughts:
Given your example data, you probably don't want that for device in inventoryObject: loop
We can drastically simplify your code by replacing that long block of conditionals with a list of attributes in which we are interested and then a for loop to extract them.
Rather than assigning a bunch of individual variables, we can build up a dictionary with the data from the queryObject
That might look like:
from xml.etree import ElementTree
import json
attributeNames = [
"mdNm",
"meNm",
"userLabel",
"resourceState",
"location",
"manufacturer",
"productName",
"version",
]
parser = ElementTree.parse("data.xml")
root = parser.getroot()
queryObjectData = root.find(".//{alu.v1}queryObjectData")
for queryObject in queryObjectData:
device = {}
for name in attributeNames:
if (value := queryObject.find(f".//{{tmf854.v1}}{name}")) is not None:
device[name] = value.text
vendorExtensions = queryObject.find("{alu.v1}vendorExtensions")
extensionMap = {}
for extension in vendorExtensions.findall(".//{alu.v1}NameAndStringValue"):
extname = extension.find("{tmf854.v1}name").text
extvalue = extension.find("{tmf854.v1}value").text
extensionMap[extname] = extvalue
device["vendorExtensions"] = extensionMap
print(json.dumps(device, indent=2))
Given your example data, this outputs:
{
"mdNm": "AMS",
"meNm": "CHEERLAVANCHA_281743",
"vendorExtensions": {
"hubSubtendedStatus": "NONE",
"productAndRelease": "DF.6.1",
"adminUserName": "isadmin"
}
}
An alternate approach, in which we just transform each queryObject into a dictionary, might look like this:
from xml.etree import ElementTree
import json
def localName(ele):
return ele.tag.split("}")[1]
def etree_to_dict(t):
if list(t):
d = {}
for child in t:
if localName(child) == "NameAndStringValue":
d.update(dict([[x.text.strip() for x in child]]))
else:
d.update({localName(child): etree_to_dict(child) for child in t})
return d
else:
return t.text.strip()
parser = ElementTree.parse("data.xml")
root = parser.getroot()
queryObjectData = root.find(".//{alu.v1}queryObjectData") or []
for queryObject in queryObjectData:
d = etree_to_dict(queryObject)
print(json.dumps(d, indent=2))
This will output:
{
"name": {
"mdNm": "AMS",
"meNm": "CHEERLAVANCHA_281743",
"ptpNm": "/type=NE/CHEERLAVANCHA_281743"
},
"vendorExtensions": {
"package": {
"hubSubtendedStatus": "NONE",
"productAndRelease": "DF.6.1",
"adminUserName": "isadmin"
}
}
}
That may or may not be appropriate depending on the structure of your real data and exactly what you're trying to accomplish.
Related
Using the xmltodict (v0.12.0) on python, I have an xml that will get parsed and converted into a json format. For example:
XML:
<test temp="temp" temp2="temp2">This is a test</test>
Will get converted to the following json:
"test": {
"#temp": "temp",
"#temp2": "temp2",
"#text": "This is a test"
}
I have a front end parser that reads JSON objects and converts them into XML. Unfortunately, the tags are required to be shaped in a different way.
What the front end parser expects:
{
test: {
"#": {
temp: "temp",
temp2: "temp2"
},
"#": "This is a test"
}
}
I feel like this formatting is better served to be modified on Python but I am having a bit of trouble iterating a much larger dictionary, where we don't know how deep an xml would go, and collecting all of the keys that start with "#" and giving that it's own object within the overall tag object. What are some ways I could approach shaping this data?
For anyone who is curious, this is how I ended up solving the issue. Like #furas stated, I decided that recursion was my best bet. I ended up iterating through my original xml data I converted to JSON with the incorrect formatting of attributes, then creating a copy while finding any attribute markers:
def structure_xml(data):
curr_dict = {}
for key,value in data.items():
if isinstance(value, dict):
curr_dict[key] = structure_xml(value)
elif isinstance(value, list):
value_list = []
for val in value:
if isinstance(val,dict) or isinstance(val,list):
value_list.append(structure_xml(val))
curr_dict[key] = value_list
else:
if '#' in key:
new_key = key.split("#",1)[1]
new_obj = { new_key: value }
if "#" in curr_dict:
curr_dict["#"][new_key] = value
else:
curr_dict["#"] = new_obj
elif '#text' in key:
curr_dict['#'] = data[key]
else:
curr_dict[key] = data[key]
return curr_dict
I'm coding a script to extract information from several XML files with the same structure but with missing sections when there is no information related to a tag. The easiest way to achieve this was using try/except so instead of getting a "AtributeError: 'NoneType' object has no atrribute 'find'" I assign an empty string('') to the object in the exeption. Something like this:
try:
string1=root.find('value1').find('value2').find('value3').text
except:
string1=''
The issue is that I want to shrink my code by using a function:
def extract(string):
tempstr=''
try:
tempstr=string.replace("\n", "")
except:
if tempstr is None:
tempstr=""
return string
And then I try to called it like this:
string1=extract(root.find('value1').find('value2').find('value3').text)
and value2 or value3 does not exist for the xml that is being processed, I get and AttributeError even if I don't use the variable in the function making the function useless.
Is there a way to make a function work, maybe there is a way to make it run without checking if the value entered is invalid?
Solution:
I'm using a mix of both answers:
def extract(root, xpath):
tempstr=''
try:
tempstr=root.findall(xpath)[0].text.replace("\n", "")
except:
tempstr=''#To avoid getting a Nonetype object
return tempstr
You can try something like that:
def extract(root, children_keys: list):
target_object = root
result_text = ''
try:
for child_key in children_keys:
target_object = target_object.find(child_key)
result_text = target_object.text
except:
pass
return result_text
You will go deeper at XML structure with for loop (children_keys - is predefined by you list of nested keys of XML - xml-path to your object).
And if error will throw inside that code - you will get '' as result.
Example XML (source):
<?xml version="1.0" encoding="UTF-8"?>
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>
<y>Don't forget me this weekend!</y>
</body>
</note>
Example:
import xml.etree.ElementTree as ET
tree = ET.parse('note.xml')
root = tree.getroot()
children_keys = ['body', 'y']
result_string = extract(root, children_keys)
print(result_string)
Output:
"Don't forget me this weekend!"
Use XPATH expression
import xml.etree.ElementTree as ET
xml1 = '''<r><v1><v2><v3>a string</v3></v2></v1></r>'''
root = ET.fromstring(xml1)
v3 = root.findall('./v1/v2/v3')
if v3:
print(v3[0].text)
else:
print('v3 not found')
xml2 = '''<r><v1><v3>a string</v3></v1></r>'''
root = ET.fromstring(xml2)
v3 = root.findall('./v1/v2/v3')
if v3:
print(v3[0].text)
else:
print('v3 not found')
output
a string
v3 not found
I have sample below XML file and I am trying to generate below JSON but I am not geeting expected result it is only add one document in dictionary.
Sample Input XML:
<results status="passed">
<num-records>2</num-records>
<records>
<volume-info>
<flexible-volume-info>
<agg-name>aggr1_split</aggregate-name>
</flexible-volume-info>
<volume-name>volume1</volume-name>
<volume-size>
<actual-size>44</actual-volume-size>
<afs-avail>90</afs-avail>
</volume-size>
</volume-info>
<volume-info>
<flexible-volume-info>
<agg-name>aggr2_split</aggregate-name>
</flexible-volume-info>
<volume-name>volume2</volume-name>
<volume-size>
<actual-size>10</actual-volume-size>
<afs-avail>14</afs-avail>
</volume-size>
</volume-info>
</records>
</results>
Expected Output:
{
"agg-name": "aggr1_split",
"volume-name": "volume1",
"actual-size": "44"
},
{
"agg-name": "aggr2_split",
"volume-name": "volume2",
"actual-size": "10"
}
Sample code:
result = {}
for child in root.iter("records"):
result['agg-name'] = child.find('volume-info/flexible-volume-info/agg-name').text
result['volume-name'] = child.find('volume-info/volume-name').text
result['actual-size'] = child.find('volume-info/volume-size/actual-size').text
print result
Your expected output would be a dictionary which contained multiple identical keys which is not possible. You either need to choose different keys for each iteration of your loop or better still have a list of dictionaries:
import xml.etree.ElementTree as ET
xml_data = """<results status="passed">
<num-records>2</num-records>
<records>
<volume-info>
<flexible-volume-info>
<agg-name>aggr1_split</agg-name>
</flexible-volume-info>
<volume-name>volume1</volume-name>
<volume-size>
<actual-size>44</actual-size>
<afs-avail>90</afs-avail>
</volume-size>
</volume-info>
<volume-info>
<flexible-volume-info>
<agg-name>aggr2_split</agg-name>
</flexible-volume-info>
<volume-name>volume2</volume-name>
<volume-size>
<actual-size>10</actual-size>
<afs-avail>14</afs-avail>
</volume-size>
</volume-info>
</records>
</results>"""
root = ET.fromstring(xml_data)
results = []
for child in root.iter("volume-info"):
result = {}
print(child)
result['agg-name'] = child.find('flexible-volume-info/agg-name').text
result['volume-name'] = child.find('volume-name').text
result['actual-size'] = child.find('volume-size/actual-size').text
results.append(result)
print(results)
This would give you:
[{'agg-name': 'aggr1_split', 'volume-name': 'volume1', 'actual-size': '44'}, {'agg-name': 'aggr2_split', 'volume-name': 'volume2', 'actual-size': '10'}]
Your XML is also badly formed, the open and closing tags do not always match.
I am trying to develop an Infobox parser in Python which supports all the languages of Wikipedia. The parser will get the infobox data and will return the data in a Dictionary.
The keys of the Dictionary will be the property which is described (e.g. Population, City name, etc...).
The problem is that Wikipedia has slightly different page contents for each language. But the most important thing is that the API response structure for each language can also be different.
For example, the API response for 'Paris' in English contains this Infobox:
{{Infobox French commune |name = Paris |commune status = [[Communes of France|Commune]] and [[Departments of France|department]] |image = <imagemap> File:Paris montage.jpg|275px|alt=Paris montage
and in Greek, the corresponding part for 'Παρίσι' is:
[...] {{Πόλη (Γαλλία) | Πόλη = Παρίσι | Έμβλημα =Blason paris 75.svg | Σημαία =Mairie De Paris (SVG).svg | Πλάτος Σημαίας =120px | Εικόνα =Paris - Eiffelturm und Marsfeld2.jpg [...]
In the second example, there isn't any 'Infobox' occurrence after the {{. Also, in the API response the name = Paris is not the exact translation for Πόλη = Παρίσι. (Πόλη means city, not name)
Because of such differences between the responses, my code fails.
Here is the code:
class WikipediaInfobox():
# Class to get and parse the Wikipedia Infobox Data
infoboxArrayUnprocessed = [] # Maintains the order which the data is displayed.
infoboxDictUnprocessed = {} # Still Contains Brackets and Wikitext coding. Will be processed more later...
language="en"
def getInfoboxDict(self, infoboxRaw): # Get the Infobox in Dict and Array form (Unprocessed)
if infoboxRaw.strip() == "":
return {}
boxLines = [line.strip().replace(" "," ") for line in infoboxRaw.splitlines()]
wikiObjectType = boxLines[0]
infoboxData = [line[1:] for line in boxLines[1:]]
toReturn = {"wiki_type":wikiObjectType}
for i in infoboxData:
key = i.split("=")[0].strip()
value = ""
if i.strip() != key + "=":
value=i.split("=")[1].strip()
self.infoboxArrayUnprocessed.append({key:value})
toReturn[key]=value
self.infoboxDictUnprocessed = toReturn
return toReturn
def getInfoboxRaw(self, pageTitle, followRedirect = False, resetOld=True): # Get Infobox in Raw Text
if resetOld:
infoboxDict = {}
infoboxDictUnprocessed = {}
infoboxArray = []
infoboxArrayUnprocessed = []
params = { "format":"xml", "action":"query", "prop":"revisions", "rvprop":"timestamp|user|comment|content" }
params["titles"] = "%s" % urllib.quote(pageTitle.encode("utf8"))
qs = "&".join("%s=%s" % (k, v) for k, v in params.items())
url = "http://" + self.language + ".wikipedia.org/w/api.php?%s" % qs
tree = etree.parse(urllib.urlopen(url))
revs = tree.xpath('//rev')
if len(revs) == 0:
return ""
if "#REDIRECT" in revs[-1].text and followRedirect == True:
redirectPage = revs[-1].text[revs[-1].text.find("[[")+2:revs[-1].text.find("]]")]
return self.getInfoboxRaw(redirectPage,followRedirect,resetOld)
elif "#REDIRECT" in revs[-1].text and followRedirect == False:
return ""
infoboxRaw = ""
if "{{Infobox" in revs[-1].text: # -> No Multi-language support:
infoboxRaw = revs[-1].text.split("{{Infobox")[1].split("}}")[0]
return infoboxRaw
def __init__(self, pageTitle = "", followRedirect = False): # Constructor
if pageTitle != "":
self.language = guess_language.guessLanguage(pageTitle)
if self.language == "UNKNOWN":
self.language = "en"
infoboxRaw = self.getInfoboxRaw(pageTitle, followRedirect)
self.getInfoboxDict(infoboxRaw) # Now the parsed data is in self.infoboxDictUnprocessed
Some parts of this code was found on this blog...
I don't want to reinvent the wheel, so maybe someone has a nice solution for multi-language support and neat parsing of the Infobox section of Wikipedia.
I have seen many alternatives, like DBPedia or some other parsers that MediaWiki recommends, but I haven't found anything that suits my needs, yet. I also want to avoid scraping the page with BeautifulSoup, because it can fail on some cases, but if it is necessary it will do.
If something isn't clear enough, please ask. I want to help as much as I can.
Wikidata is definitely the first choice these days if you want to get structured data, anyway if in the future you need to parse data from wikipedia articles, especially as you are using Python, I can recommand mwparserfromhell which is a python library aimed at parsing wikitext and that has an option to extract templates and their attributes. That won't directly fix your issue as the multiple templates in multiple languages will definitely be different but that might be useful if you continue trying to parse wikitext.
Hey friends I am generating XML data using Python libraries as follow
def multiwan_info_save(request):
data = {}
init = "init"
try:
form = Addmultiwanform(request.POST)
except:
pass
if form.is_valid():
from_sv = form.save(commit=False)
obj_get = False
try:
obj_get = MultiWAN.objects.get(isp_name=from_sv.isp_name)
except:
obj_get = False
nameservr = request.POST.getlist('nameserver_mw')
for nm in nameservr:
nameserver1, is_new = NameServer.objects.get_or_create(name=nm)
from_sv.nameserver = nameserver1
from_sv.save()
# main(init)
top = Element('ispinfo')
# comment = Comment('Generated for PyMOTW')
#top.append(comment)
all_connection = MultiWAN.objects.all()
for conn in all_connection:
child = SubElement(top, 'connection number ='+str(conn.id)+'name='+conn.isp_name+'desc='+conn.description )
subchild_ip = SubElement(child,'ip_address')
subchild_subnt = SubElement(child,'subnet')
subchild_gtwy = SubElement(child,'gateway')
subchild_nm1 = SubElement(child,'probe_server1')
subchild_nm2 = SubElement(child,'probe_server2')
subchild_interface = SubElement(child,'interface')
subchild_weight = SubElement(child,'weight')
subchild_ip.text = str(conn.ip_address)
subchild_subnt.text = str(conn.subnet)
subchild_gtwy.text = str(conn.gateway)
subchild_nm1.text = str(conn.nameserver.name)
# subchild_nm2.text = conn.
subchild_weight.text = str(conn.weight)
subchild_interface.text = str(conn.interface)
print "trying to print _____________________________"
print tostring(top)
print "let seeeeeeeeeeeeeeeeee +++++++++++++++++++++++++"
But I am getting output like follow
<ispinfo><connection number =5name=Airtelllldesc=Largets TRelecome ><ip_address>192.168.1.23</ip_address><subnet>192.168.1.23</subnet><gateway>192.168.1.23</gateway><probe_server1>192.168.99.1</probe_server1><probe_server2 /><interface>eth0</interface><weight>160</weight></connection number =5name=Airtelllldesc=Largets TRelecome ><connection number =6name=Uninordesc=Uninor><ip_address>192.166.55.23</ip_address><subnet>192.166.55.23</subnet><gateway>192.168.1.23</gateway><probe_server1>192.168.99.1</probe_server1><probe_server2 /><interface>eth0</interface><weight>160</weight></connection number =6name=Uninordesc=Uninor><connection number =7name=Airteldesc=Largets TRelecome ><ip_address>192.168.1.23</ip_address><subnet>192.168.1.23</subnet><gateway>192.168.1.23</gateway><probe_server1>192.168.99.1</probe_server1><probe_server2 /><interface>eth0</interface><weight>160</weight></connection number =7name=Airteldesc=Largets TRelecome ></ispinfo>
I just want to know that how can I write this XML in proper XML format ?
Thanks in advance
UPDATED to include simulation of both creating and printing of the XML tree
The Basic Issue
Your code is generating invalid connection tags like this:
<connection number =5name=Airtelllldesc=Largets TRelecome ></connection number =5name=Airteldesc=Largets TRelecome >
when they should look like this (I am omitting the sub-elements in between. Your code is generating these correctly):
<connection number="5" name="Airtellll" desc="Largets TRelecome" ></connection>
If you had valid XML, this code would print it neatly:
from lxml import etree
xml = '''<ispinfo><connection number="5" name="Airtellll" desc="Largets TRelecome" ><ip_address>192.168.1.23</ip_address><subnet>192.168.1.23</subnet><gateway>192.168.1.23</gateway><probe_server1>192.168.99.1</probe_server1><probe_server2 /><interface>eth0</interface><weight>160</weight></connection></ispinfo>'''
xml = etree.XML(xml)
print etree.tostring(xml, pretty_print = True)
Generating Valid XML
A small simulation follows:
from lxml import etree
# Some dummy text
conn_id = 5
conn_name = "Airtelll"
conn_desc = "Largets TRelecome"
ip = "192.168.1.23"
# Building the XML tree
# Note how attributes and text are added, using the Element methods
# and not by concatenating strings as in your question
root = etree.Element("ispinfo")
child = etree.SubElement(root, 'connection',
number = str(conn_id),
name = conn_name,
desc = conn_desc)
subchild_ip = etree.SubElement(child, 'ip_address')
subchild_ip.text = ip
# and pretty-printing it
print etree.tostring(root, pretty_print=True)
This will produce:
<ispinfo>
<connection desc="Largets TRelecome" number="5" name="Airtelll">
<ip_address>192.168.1.23</ip_address>
</connection>
</ispinfo>
A single line is proper, in the sense that a XML parser will understand it.
For pretty-printing to sys.stdout, use the dump method of Element.
For pretty-printing to a stream, use the write method of ElementTree.