xml.etree.ElementTree对CDATA的输出

xml.etree.ElmentTree不支持CDATA 的输出，但是支持Comment的输出。由于在项目中需要输出带有CDATA块的XML文本，参考Comment的做法，修改ElmentTree中的

_serialize_xml方法中。实现如下：

import xml.etree.ElementTree as ET

def CDATA(text=None):
    element = ET.Element('![CDATA[')
    element.text = text
    return element

ET._original_serialize_xml = ET._serialize_xml

def _serialize_xml(write, elem, qnames, namespaces,short_empty_elements, **kwargs):

    if elem.tag == '![CDATA[':
        #write("\n<{}{}]]>\n".format(elem.tag, elem.text))
        write("<%s%s]]>" % (elem.tag, elem.text))
        if elem.tail:
            write(ET._escape_cdata(elem.tail))
    else:
        return ET._original_serialize_xml(write, elem, qnames, namespaces,short_empty_elements, **kwargs)

ET._serialize_xml = ET._serialize['xml'] = _serialize_xml

测试代码：

text = """
<?xml version='1.0' encoding='utf-8'?>
<text>
This is just some sample text.
</text>
"""

e = ET.Element("data")
cdata = MyET.CDATA(text)
e.append(cdata)

#tests
print(ET.tostring(e,encoding="utf-8"))

结果：

b"<data><![CDATA[\n<?xml version='1.0' encoding='utf-8'?>\n<text>\nThis is just some sample text.\n</text>\n]]></data>"