Reciving a xml string from C# program unable to parse with ET.fromstring in Python 3.5

Question

I have a C# program that sends an XML string as this:

<?xml version="1.0" encoding="utf-16" standalone="no"?>
<ScoreList>
  <Player UserName="Player1" Score="10" />
  <Player UserName="Player2" Score="20" />
</ScoreList>

But when I receive it in my Python program it looks like this

   b'<?xml version="1.0" encoding="utf-16" standalone="no"?>
   \r\n<ScoreList>\r\n  
   <Player UserName="Player1" Score="10" />
   \r\n  <Player UserName="Player2" Score="20" />
   \r\n</ScoreList>'

I'm sending it to a server with this code C#

Byte[] sendBytes = Encoding.BigEndianUnicode.GetBytes(doc);
        netStream.Write(sendBytes, 0, sendBytes.Length);

And receiving with this code on the Python(Version 3.5) end

self.data = self.request.recv(1024).strip()

Then when I try to parse it using this code

tree = ET.fromstring(self.data)

I get the error:

 File "<string>", line None
 xml.etree.ElementTree.ParseError: not well-formed (invalid token): line 1, 
 column 1

Any advice on where I'm going wrong or what I could try to fix this.

Don't know much about Python but it seems you are trying to parse XML by string function. I believe there must be some XML parsing functions docs.python.org/2/library/xml.etree.elementtree.html — Hemant Sakta
– Hemant Sakta, Commented Mar 1, 2019 at 1:45
Hemant Sakta I'm using a String function because the xml is turned into string on the c# side and then I want to change it back to xml on the python side. — Kevin Moran
– Kevin Moran, Commented Mar 1, 2019 at 10:26

snakecharmerb · Accepted Answer · 2019-03-02 10:09:49Z

1

It looks as if you are calling str on a bytes instance somewhere in your code.

Consider this xml fragment:

>>> x = '<foo>Hello world</foo>'

If it is being sent across the network it will must be encoded as bytes.

>>> bs = x.encode('utf-8')
>>> bs
b'<foo>Hello world</foo>'

ElementTree will accept the UTF-8 encoded bytes as is, or you can decode them before passing them to ElementTree:

>>> decoded = bs.decode('utf-8')
>>> decoded
'<foo>Hello world</foo>'

However if you call str on the bytes, you'll get the repr of the bytes, which will include the leading b:

>>> stringified = str(bs)
>>> stringified
"b'<foo>Hello world</foo>'"

ElementTree will not accept this input:

>>> ET.fromstring(stringified)
Traceback (most recent call last):
  ...
xml.etree.ElementTree.ParseError: not well-formed (invalid token): line 1, column 1

To fix this, you need to look at how self.data is being constructed. Make sure that you are calling decode() on the bytes that you receive, rather than str().

answered Mar 2, 2019 at 10:09

snakecharmerb

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1 Comment

Kevin Moran Over a year ago

Thank You. My issue was the way I had written the decode.

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