ElementTree TypeError "write() argument must be str, not bytes" in Python3

Question

Got a Problem with generating a .SVG File with Python3 and ElementTree.

    from xml.etree import ElementTree as et
    doc = et.Element('svg', width='480', height='360', version='1.1', xmlns='http://www.w3.org/2000/svg')

    #Doing things with et and doc

    f = open('sample.svg', 'w')
    f.write('<?xml version=\"1.0\" standalone=\"no\"?>\n')
    f.write('<!DOCTYPE svg PUBLIC \"-//W3C//DTD SVG 1.1//EN\"\n')
    f.write('\"http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd\">\n')
    f.write(et.tostring(doc))
    f.close()

The Function et.tostring(doc) generates the TypeError "write() argument must be str, not bytes". I don't understand that behavior, "et" should convert the ElementTree-Element into a string? It works in python2, but not in python3. What did i do wrong?

Answer 1

As it turns out, tostring, despite its name, really does return an object whose type is bytes.

Stranger things have happened. Anyway, here's the proof:

>>> from xml.etree.ElementTree import ElementTree, tostring
>>> import xml.etree.ElementTree as ET
>>> element = ET.fromstring("<a></a>")
>>> type(tostring(element))
<class 'bytes'>

Silly, isn't it?

Fortunately you can do this:

>>> type(tostring(element, encoding="unicode"))
<class 'str'>

Yes, we all thought the ridiculousness of bytes and that ancient, forty-plus-year-old-and-obsolete encoding called ascii was dead.

And don't get me started on the fact that they call "unicode" an encoding!!!!!!!!!!!

Answer 2

The output file should be in binary mode.

f = open('sample.svg', 'wb')

Answer 3

Try:

f.write(et.tostring(doc).decode(encoding))

Example:

f.write(et.tostring(doc).decode("utf-8"))

Answer 4

Specify encoding of string while writing the xml file.

Like decode(UTF-8) with write(). Example: file.write(etree.tostring(doc).decode(UTF-8))