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I am using python to do some conditional changes to an XML document. The incoming document has <?xml version="1.0" ?> at the top.

I'm using xml.etree.ElementTree.

How I'm parsing the changed XMl:

filter_update_body = ET.tostring(root, encoding="utf8", method="xml")

The output has this at the top:

<?xml version='1.0' encoding='utf8'?>

The client wants the "encoding" tag removed but if I remove it then it either doesn't include the line at all or it puts in encoding= 'us-ascii'

Can this be done so the output matches: <?xml version="1.0" ?>?

(I don't know why it matters honestly but that's what I was told needed to happen)

mzjn
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Bryant Richards
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  • You could just write the XML to string, modify the string, and then write it out. `outxml = outxml.replace("encoding='utf8'", "", 1)` – James Jan 26 '23 at 14:47
  • I'm very new tp Python (we typically use JS and this is an edge case for us) So I did this: `filter_update_body = ET.tostring(root, encoding="utf8", method="xml") filter_update_body = filter_update_body.replace("encoding='utf8'", "", 1)` and I got an error: "TypeError: a bytes-like object is required, not 'str'" – Bryant Richards Jan 26 '23 at 15:00
  • That error isn't being caused by the string replacement. `replace` is a perfectly valid method of strings. Are you perhaps trying to write the file in binary mode? – kindall Jan 26 '23 at 15:09
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    Prefix both the strings in `replace` with `b` like this `replace(b"encoding='utf-8'", b"", 1)` – Friedrich Jan 26 '23 at 15:12
  • @Friedrich solution worked! Thank you! For my own knowledge, what does putting the `b` in there do? – Bryant Richards Jan 26 '23 at 15:15
  • `b`creates a bytes object. Which is what `bytes.replace()` asked for. It's all there, you just need to read it ;) – Friedrich Jan 26 '23 at 15:17
  • The alternative would be to call `ET.tostring(root, encoding="unicode")` and have a `str` returned. In that case, no `b`. String types in python can be tricky. The `type()` function is your friend if you want to know what you're dealing with. – Friedrich Jan 26 '23 at 15:19

1 Answers1

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As pointed out in this answer there is no way to make ElementTree omit the encoding attribute. However, as @James suggested in a comment, it can be stripped from the resulting output like this:

filter_update_body = ET.tostring(root, encoding="utf8", method="xml")
filter_update_body = filter_update_body.replace(b"encoding='utf8'", b"", 1)

The b prefixes are required because ET.tostring() will return a bytes object if encoding != "unicode". In turn, we need to call bytes.replace().

With encoding = "unicode" (note that this is the literal string "unicode"), it will return a regular str. In this case, the bs can be omitted. We use good old str.replace().

It's worth noting that the choice between bytes and str also affects how the XML will eventually be written to a file. A bytes object should be written in binary mode, a str in text mode.

Friedrich
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