In xml.etree.ElementTree bytes tag or attributes raises on serialization #72424

Activity

1. py-user commented on Sep 21, 2016

   

   py-usermannequin

   on Sep 21, 2016

   MannequinAuthor

   More actions

   https://docs.python.org/3/library/xml.etree.elementtree.html#xml.etree.ElementTree.Element
   "The element name, attribute names, and attribute values can be either bytestrings or Unicode strings."

   The element name, attribute names, and attribute values can have bytes type, but they can't be serialized:

   >>> import xml.etree.ElementTree as etree
   >>>
   >>> root = etree.Element(b'x')
   >>> root
   <Element b'x' at 0xb739934c>
   >>>
   >>> elem = etree.SubElement(root, b'y', {b'a': b'b'})
   >>> elem
   <Element b'y' at 0xb7399374>
   >>> elem.attrib
   {b'a': b'b'}
   >>>
   >>> etree.dump(root)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 1224, in dump
       elem.write(sys.stdout, encoding="unicode")
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 826, in write
       qnames, namespaces = _namespaces(self._root, default_namespace)
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 937, in _namespaces
       _raise_serialization_error(tag)
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 1105, in _raise_serialization_error
       "cannot serialize %r (type %s)" % (text, type(text).__name__)
   TypeError: cannot serialize b'x' (type bytes)
   >>>
   >>> etree.tostring(root)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 1171, in tostring
       ElementTree(element).write(stream, encoding, method=method)
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 826, in write
       qnames, namespaces = _namespaces(self._root, default_namespace)
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 937, in _namespaces
       _raise_serialization_error(tag)
     File "/usr/lib/python3.3/xml/etree/ElementTree.py", line 1105, in _raise_serialization_error
       "cannot serialize %r (type %s)" % (text, type(text).__name__)
   TypeError: cannot serialize b'x' (type bytes)
   >>>

   Also attribute name can be serialized, but it holds the letter "b" and single quotes:

   >>> import xml.etree.ElementTree as etree
   >>> 
   >>> e = etree.Element('a', {b'x': '1'})
   >>> etree.tostring(e)
   b'<a b\'x\'="1" />'
   >>>

   And same try with site package lxml works fine for all cases because it converts bytes to unicode strings right away:

   >>> import lxml.etree
   >>>
   >>> root = lxml.etree.Element(b'x')
   >>> root
   <Element x at 0xb6ff00cc>
   >>>
   >>> elem = lxml.etree.SubElement(root, b'y', {b'a': b'b'})
   >>> elem
   <Element y at 0xb73a834c>
   >>>
   >>> elem.attrib
   {'a': 'b'}
   >>>
2. py-user

   added

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   topic-XML

   type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

   on Sep 21, 2016
3. scoder commented on Sep 10, 2019

   

   scoder

   on Sep 10, 2019

   Contributor

   More actions

   Arguably, writing out "b'x'" as attribute name instead of raising an exception isn't ideal. However, OTOH, I think it's reasonable to accept anything that is serialisable as a string, not just strings. That makes it difficult to draw a line.

   In any case, it's ok for ElementTree to not allow bytes in general.

   I'll close this issue, because I don't think it's worth being called a bug.
4. scoder

   closed this as completedon Sep 10, 2019
5. ezio-melotti

   transferred this issue fromon Apr 10, 2022