Element objects have no .getroot() method. Drop that call, and the .tostring() call works:

xmlstr = ElementTree.tostring(et, encoding='utf8', method='xml')

You only need to use .getroot() if you have an ElementTree instance.

Other notes:

• This produces a bytestring, which in Python 3 is the bytes type.
  If you must have a str object, you have two options:

  1. Decode the resulting bytes value, from UTF-8: xmlstr.decode("utf8")

  2. Use encoding='unicode'; this avoids an encode / decode cycle:

     xmlstr = ElementTree.tostring(et, encoding='unicode', method='xml')
     

• If you wanted the UTF-8 encoded bytestring value or are using Python 2, take into account that ElementTree doesn't properly detect utf8 as the standard XML encoding, so it'll add a <?xml version='1.0' encoding='utf8'?> declaration. Use utf-8 or UTF-8 (with a dash) if you want to prevent this. When using encoding="unicode" no declaration header is added.

How do I convert ElementTree.Element to a String?

For Python 3:

xml_str = ElementTree.tostring(xml, encoding='unicode')

For Python 2:

xml_str = ElementTree.tostring(xml, encoding='utf-8')

The following is compatible with both Python 2 & 3, but only works for Latin characters:

xml_str = ElementTree.tostring(xml).decode()

Example usage

from xml.etree import ElementTree


xml = ElementTree.Element("Person", Name="John")
xml_str = ElementTree.tostring(xml).decode()
print(xml_str)

Output:

<Person Name="John" />

Explanation

Despite what the name implies, ElementTree.tostring() returns a bytestring by default in Python 2 & 3. This is an issue in Python 3, which uses Unicode for strings.

In Python 2 you could use the str type for both text and binary data. Unfortunately this confluence of two different concepts could lead to brittle code which sometimes worked for either kind of data, sometimes not. [...]

To make the distinction between text and binary data clearer and more pronounced, [Python 3] made text and binary data distinct types that cannot blindly be mixed together.

^{Source: Porting Python 2 Code to Python 3}

If we know what version of Python is being used, we can specify the encoding as unicode or utf-8. Otherwise, if we need compatibility with both Python 2 & 3, we can use decode() to convert into the correct type.

For reference, I've included a comparison of .tostring() results between Python 2 and Python 3.

ElementTree.tostring(xml)
# Python 3: b'<Person Name="John" />'
# Python 2: <Person Name="John" />


ElementTree.tostring(xml, encoding='unicode')
# Python 3: <Person Name="John" />
# Python 2: LookupError: unknown encoding: unicode


ElementTree.tostring(xml, encoding='utf-8')
# Python 3: b'<Person Name="John" />'
# Python 2: <Person Name="John" />


ElementTree.tostring(xml).decode()
# Python 3: <Person Name="John" />
# Python 2: <Person Name="John" />

Thanks to Martijn Peters for pointing out that the str datatype changed between Python 2 and 3.

Why not use str()?

In most scenarios, using str() would be the "cannonical" way to convert an object to a string. Unfortunately, using this with Element returns the object's location in memory as a hexstring, rather than a string representation of the object's data.

from xml.etree import ElementTree


xml = ElementTree.Element("Person", Name="John")
print(str(xml))  # <Element 'Person' at 0x00497A80>

Non-Latin Answer Extension

Extension to @Stevoisiak's answer and dealing with non-Latin characters. Only one way will display the non-Latin characters to you. The one method is different on both Python 3 and Python 2.

Input

xml = ElementTree.fromstring('<Person Name="크리스" />')
xml = ElementTree.Element("Person", Name="크리스")  # Read Note about Python 2

NOTE: In Python 2, when calling the toString(...) code, assigning xml with ElementTree.Element("Person", Name="크리스")will raise an error...

UnicodeDecodeError: 'ascii' codec can't decode byte 0xed in position 0: ordinal not in range(128)

Output

ElementTree.tostring(xml)
# Python 3 (크리스): b'<Person Name="&#53356;&#47532;&#49828;" />'
# Python 3 (John): b'<Person Name="John" />'


# Python 2 (크리스): <Person Name="&#53356;&#47532;&#49828;" />
# Python 2 (John): <Person Name="John" />




ElementTree.tostring(xml, encoding='unicode')
# Python 3 (크리스): <Person Name="크리스" />             <-------- Python 3
# Python 3 (John): <Person Name="John" />


# Python 2 (크리스): LookupError: unknown encoding: unicode
# Python 2 (John): LookupError: unknown encoding: unicode


ElementTree.tostring(xml, encoding='utf-8')
# Python 3 (크리스): b'<Person Name="\xed\x81\xac\xeb\xa6\xac\xec\x8a\xa4" />'
# Python 3 (John): b'<Person Name="John" />'


# Python 2 (크리스): <Person Name="크리스" />             <-------- Python 2
# Python 2 (John): <Person Name="John" />


ElementTree.tostring(xml).decode()
# Python 3 (크리스): <Person Name="&#53356;&#47532;&#49828;" />
# Python 3 (John): <Person Name="John" />


# Python 2 (크리스): <Person Name="&#53356;&#47532;&#49828;" />
# Python 2 (John): <Person Name="John" />

If you just need this for debugging to see how the XML looks like, then instead of print(xml.etree.ElementTree.tostring(e)) you can use dump like this:

xml.etree.ElementTree.dump(e)

And this works both with Element and ElementTree objects as e, so there should be no need for getroot.

The documentation of dump says:

xml.etree.ElementTree.dump(elem)

Writes an element tree or element structure to sys.stdout. This function should be used for debugging only.

The exact output format is implementation dependent. In this version, it’s written as an ordinary XML file.

elem is an element tree or an individual element.

Changed in version 3.8: The dump() function now preserves the attribute order specified by the user.

I had the same problem in Python 3.8 and none of the previous answers solved it. The issue is that ElementTree is both the name of a module and of a class within it. Using an alias makes it clear:

from xml.etree.ElementTree import ElementTree
import xml.etree.ElementTree as XET
...
ElementTree.tostring(...)  # Attribute-error
XET.tostring(...)          # Works

Input Sample File Content:

<?xml version="1.0" encoding="ISO-8859-1"?>
<UPDATE>
<DATA><SET_DOC ID="249865"/></DATA>
</UPDATE>

To String approach code for specific element:

import lxml.etree as ET


samplexml = ET.parse(r"D:\sample.xml")


sampleroot = samplexml.getroot()


for dataElement in sampleroot.iter('DATA'):
updatext = ET.tostring(dataElement)
print(updatext)

Output:

b'<DATA><SET_DOC ID="249865"/></DATA>\n'