无法转储或写入 ElementTree 元素

发布于 2024-11-18 00:20:35 字数 458 浏览 1 评论 0原文

我在输出即使是最简单的元素（树）实例时也遇到问题。如果我在 Python 2.7.1 中尝试以下代码，

>>> from xml.etree.ElementTree import Element, SubElement, tostring
>>> root = Element('parent')
>>> child = Element('child')
>>> SubElement(root, child)
>>> tostring(root)

则会收到错误：

TypeError: cannot serialize <Element 'root' at 0x9a7c7ec> (type Element)

我一定做错了什么，但文档没有向我指出任何明显的事情。

原文

I'm having a problem outputting even the simplest Element(Tree) instances. If I try the following code in Python 2.7.1

>>> from xml.etree.ElementTree import Element, SubElement, tostring
>>> root = Element('parent')
>>> child = Element('child')
>>> SubElement(root, child)
>>> tostring(root)

I get an error:

TypeError: cannot serialize <Element 'root' at 0x9a7c7ec> (type Element)

I must be doing something wrong but the documentation isn't pointing me at anything obvious.

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回忆凄美了谁 2024-11-25 00:20:35

SubElement 不将元素作为第二个参数。 API 文档给出签名，即

SubElement(parent, tag, attrib={}, **extra)

第二个参数是子元素的标签（即名称）

ElementTree 文档提供更多详细信息

要添加子元素，请查看附加内容元素上的方法，例如

root.append(child)

SubElement does not take an element as the second parameter. The API docs give the signature as

SubElement(parent, tag, attrib={}, **extra)

i.e. the second parameter is the tag (i.e. name) of the sub element

The ElementTree docs give more detail

To add a child element look at the append method on Element e.g.

root.append(child)

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反差帅 2024-11-25 00:20:35

http://docs.python.org/library /xml.etree.elementtree.html#xml.etree.ElementTree.SubElement

SubElement 的第二个参数是 tag (str) 而不是 Element，它自己创建 Element 实例：

>>> SubElement(root, 'child')
0: <Element 'child' at 0x1f2dfb0>
>>> tostring(root)
1: '<parent><child /></parent>'

http://docs.python.org/library/xml.etree.elementtree.html#xml.etree.ElementTree.SubElement

SubElement's second argument is tag (str) not Element, it creates Element instance by itself:

>>> SubElement(root, 'child')
0: <Element 'child' at 0x1f2dfb0>
>>> tostring(root)
1: '<parent><child /></parent>'

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无所谓啦 2024-11-25 00:20:35

问题很老了，但也许这句话会对某人有所帮助：
当使用例如 lxml 创建 XML 对象并且从另一个库调用 .tostring 时，也可能会抛出“无法序列化”

（脏）解决方案的示例（没有针对此处显示的无效参数的保护）

inxml = elxml.getroot() if hasattr(elxml, 'getroot') else elxml
try:
    from lxml import etree as ETS
    outstr = ETS.tostring(inxml)
except:
    try:
        import xml.etree.cElementTree as ETS
    except:
        import xml.etree.ElementTree as ETS
    outstr = ETS.tostring(inxml)
return outstr

Problem is pretty old but maybe this remark will help someone:
'cannot serialize' can be thrown also when XML object was created with e.g. lxml and .tostring is called from another library, e.g. xml.etree.ElementTree

Example of (dirty) solution (no protection against invalid args shown here)

inxml = elxml.getroot() if hasattr(elxml, 'getroot') else elxml
try:
    from lxml import etree as ETS
    outstr = ETS.tostring(inxml)
except:
    try:
        import xml.etree.cElementTree as ETS
    except:
        import xml.etree.ElementTree as ETS
    outstr = ETS.tostring(inxml)
return outstr

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