python - lxml: insert tag at a given position

Question

I have an xml file, similar to this:

<tag attrib1='I'>
  <subtag1 subattrib1='1'>
    <subtext>text1</subtext>
  </subtag1>
  <subtag3 subattrib3='3'>
    <subtext>text3</subtext>
  </subtag3>
</tag>

I would like to insert a new subElement, so the result would be something like this

<tag attrib1='I'>
  <subtag1 subattrib1='1'>
    <subtext>text1</subtext>
  </subtag1>
  <subtag2 subattrib2='2'>
    <subtext>text2</subtext>
  </subtag2>
  <subtag3 subattrib3='3'>
    <subtext>text3</subtext>
  </subtag3>
</tag>

I can append my xml file, but then the new elements will be inserted at the end. How can I force python lxml to put it into a given position?

Thanks for your help!

Answer 1

You can use the addnext() method:

from lxml import etree

XML= """
<tag attrib1='I'>
  <subtag1 subattrib1='1'>
    <subtext>text1</subtext>
  </subtag1>
  <subtag3 subattrib3='3'>
    <subtext>text3</subtext>
  </subtag3>
</tag>"""

parser = etree.XMLParser(remove_blank_text=True)
tag = etree.fromstring(XML, parser)

subtag1 = tag.find("subtag1")
subtag2 = etree.Element("subtag2", subattrib2="2")
subtext = etree.SubElement(subtag2, "subtext")
subtext.text = "text2"
subtag1.addnext(subtag2)   # Add subtag2 as a following sibling of subtag1

print etree.tostring(tag, pretty_print=True)

Output:

<tag attrib1="I">
  <subtag1 subattrib1="1">
    <subtext>text1</subtext>
  </subtag1>
  <subtag2 subattrib2="2">
    <subtext>text2</subtext>
  </subtag2>
  <subtag3 subattrib3="3">
    <subtext>text3</subtext>
  </subtag3>
</tag>

Alternative: use insert() on the root element:

subtag2 = etree.Element("subtag2", subattrib2="2")
subtext = etree.SubElement(subtag2, "subtext")
subtext.text = "text2"
tag.insert(1, subtag2)   # Add subtag2 as the second child (index 1) of the root element