how to remove an element in lxml

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Question :

how to remove an element in lxml

I need to completely remove elements, based on the contents of an attribute, using python’s lxml. Example:

import lxml.etree as et

xml="""
<groceries>
  <fruit state="rotten">apple</fruit>
  <fruit state="fresh">pear</fruit>
  <fruit state="fresh">starfruit</fruit>
  <fruit state="rotten">mango</fruit>
  <fruit state="fresh">peach</fruit>
</groceries>
"""

tree=et.fromstring(xml)

for bad in tree.xpath("//fruit[@state='rotten']"):
  #remove this element from the tree

print et.tostring(tree, pretty_print=True)

I would like this to print:

<groceries>
  <fruit state="fresh">pear</fruit>
  <fruit state="fresh">starfruit</fruit>
  <fruit state="fresh">peach</fruit>
</groceries>

Is there a way to do this without storing a temporary variable and printing to it manually, as:

newxml="<groceries>n"
for elt in tree.xpath('//fruit[@state='fresh']'):
  newxml+=et.tostring(elt)

newxml+="</groceries>"
Asked By: ewok

||

Answer #1:

Use the remove method of an xmlElement :

tree=et.fromstring(xml)

for bad in tree.xpath("//fruit[@state='rotten']"):
  bad.getparent().remove(bad)     # here I grab the parent of the element to call the remove directly on it

print et.tostring(tree, pretty_print=True, xml_declaration=True)

If I had to compare with the @Acorn version, mine will work even if the elements to remove are not directly under the root node of your xml.

Answered By: ewok

Answer #2:

You’re looking for the remove function. Call the tree’s remove method and pass it a subelement to remove.

import lxml.etree as et

xml="""
<groceries>
  <fruit state="rotten">apple</fruit>
  <fruit state="fresh">pear</fruit>
  <punnet>
    <fruit state="rotten">strawberry</fruit>
    <fruit state="fresh">blueberry</fruit>
  </punnet>
  <fruit state="fresh">starfruit</fruit>
  <fruit state="rotten">mango</fruit>
  <fruit state="fresh">peach</fruit>
</groceries>
"""

tree=et.fromstring(xml)

for bad in tree.xpath("//fruit[@state='rotten']"):
    bad.getparent().remove(bad)

print et.tostring(tree, pretty_print=True)

Result:

<groceries>
  <fruit state="fresh">pear</fruit>
  <fruit state="fresh">starfruit</fruit>
  <fruit state="fresh">peach</fruit>
</groceries>
Answered By: Cédric Julien

Answer #3:

I met one situation:

<div>
    <script>
        some code
    </script>
    text here
</div>

div.remove(script) will remove the text here part which I didn’t mean to.

following the answer here, I found that etree.strip_elements is a better solution for me, which you can control whether or not you will remove the text behind with with_tail=(bool) param.

But still I don’t know if this can use xpath filter for tag. Just put this for informing.

Here is the doc:

strip_elements(tree_or_element, *tag_names, with_tail=True)

Delete all elements with the provided tag names from a tree or
subtree. This will remove the elements and their entire subtree,
including all their attributes, text content and descendants. It
will also remove the tail text of the element unless you
explicitly set the with_tail keyword argument option to False.

Tag names can contain wildcards as in _Element.iter.

Note that this will not delete the element (or ElementTree root
element) that you passed even if it matches. It will only treat
its descendants. If you want to include the root element, check
its tag name directly before even calling this function.

Example usage::

   strip_elements(some_element,
       'simpletagname',             # non-namespaced tag
       '{http://some/ns}tagname',   # namespaced tag
       '{http://some/other/ns}*'    # any tag from a namespace
       lxml.etree.Comment           # comments
       )
Answered By: Acorn

Answer #4:

As already mentioned, you can use the remove() method to delete (sub)elements from the tree:

for bad in tree.xpath("//fruit[@state='rotten']"):
  bad.getparent().remove(bad)

But it removes the element including its tail, which is a problem if you are processing mixed-content documents like HTML:

<div><fruit state="rotten">avocado</fruit> Hello!</div>

Becomes

<div></div>

Which is I suppose what you not always want 🙂
I have created helper function to remove just the element and keep its tail:

def remove_element(el):
    parent = el.getparent()
    if el.tail.strip():
        prev = el.getprevious()
        if prev:
            prev.tail = (prev.tail or '') + el.tail
        else:
            parent.text = (parent.text or '') + el.tail
    parent.remove(el)

for bad in tree.xpath("//fruit[@state='rotten']"):
    remove_element(bad)

This way it will keep the tail text:

<div> Hello!</div>
Answered By: zephor

Answer #5:

You could also use html from lxml to solve that:

from lxml import html

xml="""
<groceries>
  <fruit state="rotten">apple</fruit>
  <fruit state="fresh">pear</fruit>
  <fruit state="fresh">starfruit</fruit>
  <fruit state="rotten">mango</fruit>
  <fruit state="fresh">peach</fruit>
</groceries>
"""

tree = html.fromstring(xml)

print("//BEFORE")
print(html.tostring(tree, pretty_print=True).decode("utf-8"))

for i in tree.xpath("//fruit[@state='rotten']"):
    i.drop_tree()

print("//AFTER")
print(html.tostring(tree, pretty_print=True).decode("utf-8"))

It should output this:

//BEFORE
<groceries>
  <fruit state="rotten">apple</fruit>
  <fruit state="fresh">pear</fruit>
  <fruit state="fresh">starfruit</fruit>
  <fruit state="rotten">mango</fruit>
  <fruit state="fresh">peach</fruit>
</groceries>


//AFTER
<groceries>

  <fruit state="fresh">pear</fruit>
  <fruit state="fresh">starfruit</fruit>

  <fruit state="fresh">peach</fruit>
</groceries>
Answered By: Messa

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