Writing lxml.etree with double quotes header attributes

Question

I have created a basic xml tree using lxml tutorial:

from lxml import etree
root = etree.Element("root")
root.append( etree.Element("child1") )
child2 = etree.SubElement(root, "child2")
child3 = etree.SubElement(root, "child3")
print(etree.tostring(root, pretty_print=True, encoding="UTF-8", xml_declaration=True))

This produces the following:

<?xml version='1.0' encoding='UTF-8'?>
<root>
  <child1/>
  <child2/>
  <child3/>
</root>

My question is, how to produce xml file with double quoted file header, i.e.

<?xml version="1.0" encoding="UTF-8"?>
....

Answer 1

To add the header without concatenate manually you need to use the "doctype" parameter in tostring method as bellow:

        with open(output_file, 'wb') as o:
            o.write(etree.tostring(
                document_root, pretty_print=True,
                doctype='<?xml version="1.0" encoding="ISO-8859-1"?>'
            ))