从lxml.objectify.ObjectifiedElement中剥离Python命名空间属性

Question

可能重复的问题：
使用lxml时，XML能否在没有命名空间属性的情况下渲染？

我该如何去掉一个 lxml.objectify.ObjectifiedElement 中的Python属性呢？

示例：

In [1]: from lxml import etree, objectify
In [2]: foo = objectify.Element("foo")
In [3]: foo.bar = "hi"
In [4]: foo.baz = 1
In [5]: foo.fritz = None
In [6]: print etree.tostring(foo, pretty_print=True)
<foo xmlns:py="http://codespeak.net/lxml/objectify/pytype" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" py:pytype="TREE">
  <bar py:pytype="str">hi</bar>
  <baz py:pytype="int">1</baz>
  <fritz xsi:nil="true"/>
</foo>

我希望输出的结果看起来像这样：

<foo>
  <bar>hi</bar>
  <baz>1</baz>
  <fritz/>
</foo>

Answer 1

你可以通过使用 etree.strip_attributes 和 etree.cleanup_namespaces 来实现这个功能。

In [8]: etree.strip_attributes(foo, '{http://codespeak.net/lxml/objectify/pytype}pytype')
In [9]: print etree.tostring(foo, pretty_print=True)
<foo xmlns:py="http://codespeak.net/lxml/objectify/pytype" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <bar>hi</bar>
  <baz>1</baz>
  <fritz xsi:nil="true"/>
</foo>

In [10]: etree.cleanup_namespaces(foo)
In [11]: print etree.tostring(foo, pretty_print=True)
<foo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <bar>hi</bar>
  <baz>1</baz>
  <fritz xsi:nil="true"/>
</foo>

不过，这样做还会留下 xsi:nil 的引用，你可以用类似的方法把它去掉。

In [12]: etree.strip_attributes(foo, '{http://www.w3.org/2001/XMLSchema-instance}nil')
In [13]: etree.cleanup_namespaces(foo)
In [14]: print etree.tostring(foo, pretty_print=True)
<foo>
  <bar>hi</bar>
  <baz>1</baz>
  <fritz/>
</foo>

Answer 2

还有一个专门的函数叫做 objectify.deannotate(...):

Help on built-in function deannotate in module lxml.objectify:

      deannotate(...)
        deannotate(element_or_tree, pytype=True, xsi=True, xsi_nil=False, cleanup_namespaces=False)

        Recursively de-annotate the elements of an XML tree by removing 'py:pytype'
        and/or 'xsi:type' attributes and/or 'xsi:nil' attributes.

        If the 'pytype' keyword argument is True (the default), 'py:pytype'
        attributes will be removed. If the 'xsi' keyword argument is True (the
        default), 'xsi:type' attributes will be removed.
        If the 'xsi_nil' keyword argument is True (default: False), 'xsi:nil'
        attributes will be removed.

        Note that this does not touch the namespace declarations by
        default.  If you want to remove unused namespace declarations from
        the tree, pass the option ``cleanup_namespaces=True``.