How to remove attribute from root element in Pytho

问题:

My file contains the following data:

Original:

<?xml version="1.0" encoding="UTF-8"?><urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"> <url> <changefreq>daily</changefreq> <loc>http://www.example.com</loc></url></urlset>

Expected:

<?xml version="1.0" encoding="UTF-8"?><urlset> <url> <changefreq>daily</changefreq> <loc>http://www.example.com</loc></url></urlset>

I use etree to parse the file and I want to remove the attribute from the root element 'urlset'

import xml.etree.ElementTree as ET

tree = ET.parse("/Users/hsyang/Downloads/VI-0-11-14-2016_20.xml")
root = tree.getroot()

print root.attrib
>> {}

root.attrib.pop("xmlns", None)

print root.attrib
>> {}
ET.tostring(root)

I thought I was supposed to get {xmlns:"http://www.sitemaps.org/schemas/sitemap/0.9"} when i print root.attrib the first time but I got an empty dictionary. Can someone help?

Appreciate it!

回答1:

xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" looks like a regular attribute but it is a special case, namely a namespace declaration.

Removing, adding, or modifying namespaces can be quite hard. "Normal" attributes are stored in an element's writable attrib property. Namespace mappings on the other hand are not readily available via the API (in the lxml library, elements do have a nsmap property, but it is read-only).

I suggest a simple textual search-and-replace operation, similar to the answer to Modify namespaces in a given xml document with lxml. Something like this:

with open("input.xml", "r") as infile, open("output.xml", "w") as outfile:
    data = infile.read()
    data = data.replace(' xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"', '')
    outfile.write(data)

See also How to insert namespace and prefixes into an XML string with Python?.

回答2:

In standard library xml.etree.ElementTree there is no special method to remove an attribute, but all attributes are stored in a attrib which is a dict and any attribute can be removed from attrib as a key from a dict:

    import xml.etree.ElementTree as ET

    tree = ET.parse(file_path)
    root = tree.getroot()      

    print(root.attrib)  # {'xyz': '123'}

    root.attrib.pop("xyz", None)  # None is to not raise an exception if xyz does not exist

    print(root.attrib)  # {}

    ET.tostring(root)
    '<urlset> <url> <changefreq>daily</changefreq> <loc>http://www.example.com</loc></url></urlset>'