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

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>'