python - 使用 lxml 在根元素之前/之后访问处理指令

Question

使用lxml，我如何访问/迭代位于根打开标记之前或根关闭标记之后的处理指令？

我试过这个，但是，根据文档，它只在根元素内迭代：

import io

from lxml import etree

content = """\
<?before1?>
<?before2?>
<root>text</root>
<?after1?>
<?after2?>
"""

source = etree.parse(io.StringIO(content))

print(etree.tostring(source, encoding="unicode"))
# -> <?before1?><?before2?><root>text</root><?after1?><?after2?>

for node in source.iter():
    print(type(node))
# -> <class 'lxml.etree._Element'>

我唯一的解决方案是用虚拟元素包装 XML：

dummy_content = "<dummy>{}</dummy>".format(etree.tostring(source, encoding="unicode"))
dummy = etree.parse((io.StringIO(dummy_content)))

for node in dummy.iter():
    print(type(node))
# -> <class 'lxml.etree._Element'>
#    <class 'lxml.etree._ProcessingInstruction'>
#    <class 'lxml.etree._ProcessingInstruction'>
#    <class 'lxml.etree._Element'>
#    <class 'lxml.etree._ProcessingInstruction'>
#    <class 'lxml.etree._ProcessingInstruction'>

有更好的解决方案吗？

Answer 1

您可以在根元素上使用getprevious()and方法。getnext()

before2 = source.getroot().getprevious()
before1 = before2.getprevious()

after1 = source.getroot().getnext()
after2 = after1.getnext()

请参阅https://lxml.de/api/lxml.etree._Element-class.html。

---

也可以使用 XPath（在ElementTreeorElement实例上）：

before = source.xpath("preceding-sibling::node()")  # List of two PIs
after = source.xpath("following-sibling::node()")