XML header getting removed after processing with elementtree

Question

i have an xml file and i used Elementtree to add a new tag to the xml file.My xml file before processing is as follows

<?xml version="1.0" encoding="utf-8"?>

<PackageInfo xmlns="http://someurlpackage">


<data ID="http://someurldata1">data1</data >
<data ID="http://someurldata2">data2</data >
<data ID="http://someurldata3">data3</data >
</PackageInfo>

I used following python code to add a new data tag and write it to my xml file

 tree = ET.ElementTree(xmlFile)
 root = tree.getroot()
 elem= ET.Element('data')
 elem.attrib['ID']="http://someurldata4"
 elem.text='data4'
 root[1].append(elem)
 tree = ET.ElementTree(root)
 tree.write(xmlFile)

But the resultant xml file have <?xml version="1.0" encoding="utf-8"?> absent and the file looks as below

<PackageInfo xmlns="http://someurlpackage">
<data ID="http://someurldata1">data1</data >
<data ID="http://someurldata2">data2</data >
<data ID="http://someurldata3">data3</data >
</PackageInfo>

Is there any way to include the xml header rather than hardcoding the line

Trimolecular

The prolog (<?xml ... ?>) is optional, the values in it the default. Are you sure you need it? – Zapata

yes i need it Is there any other way rather than hardfixing Thanks – Trimolecular

@user1654136 the other option is to update to a more recent Python. – Allargando

Answer 1

It looks like you need optional arguments to the write method to output the declaration.

http://docs.python.org/library/xml.etree.elementtree.html#elementtree-elementtree-objects

tree.write(xmlfile,xml_declaration=True)

---

I'm afraid I'm not that familiar with xml.etree.ElementTree and it's variation between python releases.

Here's it working with lxml.etree:

>>> from lxml import etree
>>> sample = """<?xml version="1.0" encoding="utf-8"?>
... <PackageInfo xmlns="http://someurlpackage">
... <data ID="http://someurldata1">data1</data >
... <data ID="http://someurldata2">data2</data >
... <data ID="http://someurldata3">data3</data >
... </PackageInfo>"""
>>>
>>> doc = etree.XML(sample)
>>> data = doc.makeelement("data")
>>> data.attrib['ID'] = 'http://someurldata4'
>>> data.text = 'data4'
>>> doc.append(data)
>>> etree.tostring(doc,xml_declaration=True)
'<?xml version=\'1.0\' encoding=\'ASCII\'?>\n<PackageInfo xmlns="http://someurlpackage">\n<data ID="http://someurldata1">data1</data>\n<data ID="http://someurldata2">data2</data>\n<data ID="http://someurldata3">data3</data>\n<data ID="http://someurldata4">data4</data></PackageInfo>'
>>> etree.tostring(doc,xml_declaration=True,encoding='utf-8')
'<?xml version=\'1.0\' encoding=\'utf-8\'?>\n<PackageInfo xmlns="http://someurlpackage">\n<data ID="http://someurldata1">data1</data>\n<data ID="http://someurldata2">data2</data>\n<data ID="http://someurldata3">data3</data>\n<data ID="http://someurldata4">data4</data></PackageInfo>'

Bergman

iam getting following error but iam using python 2.6 "write() got an unexpected keyword argument 'xml_declaration'" – Trimolecular

@user1654136: what library are you using? – Bergman

The Python 2.6 docs don't include the xml_declaration argument: it was presumably added later. So I think the full answer is that with the 2.6 version of ElementTree you only get the declaration when it is needed, you can't force it. – Allargando

@user1654136: If you are on python 2.6, use lxml as a (faster) alternative to the elementtree module. Same API, including the xml_declaration option, as the ElementTree module. – Zapata

Answer 2

try this:::

tree.write(xmlFile, encoding="utf-8")

Beeck

Tried it on Red Hat Linux release 7.0 (Guinness) along w/ Python2.5 it doesn't embed the XML deceleration ... – Reynaud

Answer 3

If you are using python <=2.6
There is no xml_declaration parameter in ElementTree.write()

def write(self, file, encoding="us-ascii"): 
def _write(self, file,node, encoding, namespaces):

You can use lxml.etree
install lxml
sample here:

from lxml import etree
document = etree.Element('outer')
node = etree.SubElement(document, 'inner')
print(etree.tostring(document, xml_declaration=True))

BTW:
I find that it is not necessary to write the xml_declaration
Is the XML declaration node mandatory?

There is no XML declaration necessary for a document to be successfully readable, since there are defaults for both version and encoding (1.0 and UTF-8, respectively).

At least,it works even if AndroidManifest.xml does not have an xml_declaration
I have tried :-)

Ymir