[FIXED] Beautifulsoup append ignores namespace (xml)

Issue

Hi I want to add single pictures to an existing pictures tag. I am doing it like this

for i, el in enumerate(data.get("pictures").get('picture')):
    img_link = el.get("link")[0].get('href')
    test = BeautifulSoup("""
            <pic:picture>
        <pic:link rel="thumbnail"
            href="xxxx" />
    </pic:picture>
    
    """, "xml")
    soup.ad.pictures.append(test)
print(soup.ad.pictures)

The result looks like this:

<pic:pictures>
<picture>
<link href="xxxx" rel="thumbnail"/>
</picture><picture>
<link href="xxxx" rel="thumbnail"/>
</picture><picture>
<link href="xxxx" rel="thumbnail"/>
</picture><picture>
<link href="xxxx" rel="thumbnail"/>
</picture></pic:pictures>

Why are the namespaces gone? I tried before to use new_tag and there are namespaces in there. Adding pic:pictures works fine with new_tag method but I was not able to add pic:link to pic:pictures.

Solution

The problem is how you create the new tag.

When you create a new tag using BeautifulSoup() you will lose all XML namespaces. Consider this example:

from bs4 import BeautifulSoup

main_xml = '''\
<tag xmlns:ns1="http://namespace1/" xmlns:ns2="http://namespace2/">
    <ns1:child>I'm in namespace 1</ns1:child>
    <ns2:child>I'm in namespace 2</ns2:child>
</tag>'''


soup = BeautifulSoup(main_xml, 'xml')

# add tag created by BeautifulSoup() constructor
test = BeautifulSoup("""<ns1:child>New Tag</ns1:child>""", "xml")
soup.tag.append(test)

print(soup)

Prints:

<?xml version="1.0" encoding="utf-8"?>
<tag xmlns:ns1="http://namespace1/" xmlns:ns2="http://namespace2/">
<ns1:child>I'm in namespace 1</ns1:child>
<ns2:child>I'm in namespace 2</ns2:child>
<child>New Tag</child>
</tag>

You see the newly appended tag doesn't have any namespace

---

However, if you create new tag using soup.new_tag() method the namespaces are not lost (because soup object already knows about them):

# add tag created by .new_tag() method
test = soup.new_tag('ns1:child')
test.string = "I'm new tag!"
soup.tag.append(test)

print(soup)

Prints:

<?xml version="1.0" encoding="utf-8"?>
<tag xmlns:ns1="http://namespace1/" xmlns:ns2="http://namespace2/">
<ns1:child>I'm in namespace 1</ns1:child>
<ns2:child>I'm in namespace 2</ns2:child>
<ns1:child>I'm new tag!</ns1:child>
</tag>

Answered By - Andrej Kesely