ElementTree TypeError"write()参数必须是str，而不是字节"在Python3中

问题描述

遇到了使用Python3和ElementTree生成.SVG文件的问题.

    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()

函数et.tostring(doc)生成TypeError"write()参数必须为str，而不是字节".我不了解这种行为，"et"应该将ElementTree-Element转换为字符串吗?它适用于python2，但不适用于python3.我做错了什么?

解决方案

事实证明，tostring，尽管它的名字，实际上确实返回了一个对象，该对象的类型是bytes.

发生了奇怪的事情.无论如何，这是证明:

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

傻，不是吗?

幸运的是，您可以这样做:

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

是的，我们都认为字节的荒谬之处以及被称为ascii的古老，已有40多年历史的过时编码了.

不要让我开始，因为他们称"unicode"为编码！

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?

解决方案

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!!!!!!!!!!!

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