How to append comment to XML file after XML declaration using Python?

Question

I create a root:

from xml.etree.ElementTree import Element, tostring

root = Element("root")

Then generating a string repr of XML:

xmlstr = tostring(root, encoding="utf8", method="xml")

And create my xml file:

        myFile = open(file, "w")
        myFile.write(xmlstr)
        myFile.close()

After all operations my file looks like that:

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

What I should do to add some comments after xml declaration? Tried to use xml.etree.ElementTree.Comment but not sure how to do it properly. My desirable file should looks:

<?xml version="1.0" encoding="UTF-8"?>
<!-- My comments -->
<root>
</root>

Feel free to ask if you don't understand something. Thanks!

With lxml instead of ElementTree, you can use getprevious(). See stackoverflow.com/q/69652602/407651 and stackoverflow.com/q/23025245/407651 — mzjn
– mzjn, Commented Jun 29, 2022 at 11:38
If you cannot use lxml, maybe you can read the file as plain text (not parsed XML) to add your comment after the first line, as suggested here: stackoverflow.com/a/69653155/407651 — mzjn
– mzjn, Commented Jun 29, 2022 at 12:58

mzjn · Accepted Answer · 2022-06-30 06:51:41Z

0

Here is a suggestion. Provide both the XML declaration and the comment as a "header" string.

from xml.etree.ElementTree import Element, tostring

header = """<?xml version="1.0" encoding="UTF-8"?>
<!-- My comments -->
"""

root = Element("root")
xmlstr = tostring(root).decode()

# Create a file with header + xmlstr
with open("out.xml", "w", encoding='UTF-8') as out:
    out.write(header + xmlstr)

Resulting content in out.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!-- My comments -->
<root />

answered Jun 30, 2022 at 6:51

mzjn

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4 Comments

user19263504 Over a year ago

Will check it and let you know ;)

user19263504 Over a year ago

Almost perfect, <?xml version="1.0" encoding="UTF-8"?>  <root> As you can see, there are additionaly tabs. How can I remove them? Maybe strip func?

mzjn Over a year ago

Not sure I understand. I don't get any tabs, but there are line breaks. The output is almost exactly what you call "My desirable file".

user19263504 Over a year ago

Yes, I made mistake by my side, everything is ok! ;) Thank you a lot for help!

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