在Python中使用ElementTree添加兄弟元素

Question

有了这样的XML内容：

<a>
  <b>
  </b>
</a>

我需要添加一个兄弟节点，类似于：

<a>
  <b>
  </b>
  <b'>
  </b'>
</a>

ElementTree有没有可以添加兄弟节点的功能？如果没有的话，我想我需要一个函数来获取父节点，然后添加一个子节点，我该怎么做呢？

Answer 1

根据现有的内容：

import re

def sibling(bal,text):
    print 'bal ==' + bal + '\n' # + '\n\n' + s

    def aux(match):
        # match.group(4) is '/' or None    
        return ("%s%s<%s'/>%s" % match.group(1,2,3,6) if match.group(4)
                else "%s%s<%s'>%s'>%s" % match.group(1,2,3,5,6))

    return re.sub('('
                  '(^\s*)<(' + bal + ')(?: [^/>]+)?'  # 2 and 3
                  '(?:(/)|>(?:.*?)((?:(?:\n|\r\n?)\\2)?</\\3))' # 4 and 5
                  '>(\n|\r\n?|\Z)' # 6
                  ')',
                  aux, text, flags = re.MULTILINE|re.DOTALL)


ch = """\
<a>
  <b>
  </b>
</a>
"""

dh = """\
<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
      </FECS>
    </OTF>
</entry>
"""

print sibling('a',ch)
print '------------------------------------------------------'
print sibling('b',ch)
print '------------------------------------------------------'

for x in ('entry','dd:country_code','content','OTF','FECS',
          'BackEndCompatibility','BackEnd','Forth'):
    print sibling(x,dh)
    print '------------------------------------------------------'

结果是：

bal ==a

<a>
  <b>
  </b>
</a>
<a'>
</a'>

------------------------------------------------------
bal ==b

<a>
  <b>
  </b>
  <b'>
  </b'>
</a>

------------------------------------------------------
bal ==entry

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
      </FECS>
    </OTF>
</entry>
<entry'>
</entry'>

------------------------------------------------------
bal ==dd:country_code

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <dd:country_code'></dd:country_code'>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
      </FECS>
    </OTF>
</entry>

------------------------------------------------------
bal ==content

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <content'></content'>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
      </FECS>
    </OTF>
</entry>

------------------------------------------------------
bal ==OTF

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
      </FECS>
    </OTF>
    <OTF'>
    </OTF'>
</entry>

------------------------------------------------------
bal ==FECS

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
      </FECS>
      <FECS'>
      </FECS'>
    </OTF>
</entry>

------------------------------------------------------
bal ==BackEndCompatibility

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
        <BackEndCompatibility'>
        </BackEndCompatibility'>
      </FECS>
    </OTF>
</entry>

------------------------------------------------------
bal ==BackEnd

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <BackEnd'/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
        </BackEndCompatibility>
      </FECS>
    </OTF>
</entry>

------------------------------------------------------
bal ==Forth

<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xmlns:dd="http://example.com/ns/1.0" xml:lang="en-US">
<entry>
    <dd:country_code>USA</dd:country_code>
    <content type="html">Hello World!</content>
    <OTF>
      <FECS state="disabled" version="2.2.0.0">
        <BackEndCompatibility major="2.2" state="disabled">
            <BackEnd state="disabled" version="2.2.0.0"/>
            <Forth type="ziwi">d,;%er*dkj@jkber-uyr</Forth>
            <Forth'></Forth'>
        </BackEndCompatibility>
      </FECS>
    </OTF>
</entry>

------------------------------------------------------

它对 'a' 有效，并且

"""\
<a>
  <b>
  </b>
</a>
"""

但是对

"""\
<a>
  <b>
  </b>
</a>"""

Answer 2

Python标准库里自带的ElementTree实现没有办法直接获取一个节点的父节点。

不过，如果你使用的是lxml的etree实现，那就有一个叫做getparent()的方法，可以用来获取父节点。

Answer 3

在标准库的版本中，你不能直接访问父节点。你需要从父节点开始往下找，或者自己记录父子关系。可以看看这些建议（这是这个库作者提供的）。

不过，如果你使用lxml，就有一个叫getparent()的方法（你还可以用getnext()和getprevious()），而且更方便的是，还有addnext()和addprevious()这两个方法。

所以，选择其中一个解决方案，取决于你使用的是哪个ElementTree的实现（或者你甚至可以考虑换一种实现）。