XML header getting removed after processing with elementtree

问题

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

回答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>'

回答2:

try this:::

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

回答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 :-)

来源：https://stackoverflow.com/questions/12457400/xml-header-getting-removed-after-processing-with-elementtree

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