How to use Python XML findall to find '<v:imagedata r:id=“rId7” o:title=“1-REN”/>'

问题

I'm trying to do a find all from a Word document for <v:imagedata r:id="rId7" o:title="1-REN"/> with namespace xmlns:v="urn:schemas-microsoft-com:vml" and I cannot figure out what on earth the syntax is.

The docs only cover the very straight forward case and with the URN and VML combo thrown in I can't seem to get any of the examples I've seen online to work. Does anyone happen to know what it is?

I'm trying to do something like this:

namespace = {'v': "urn:schemas-microsoft-com:vml"}

results = ET.fromstring(xml).findall("imagedata", namespace)
for image_id in results:
    print(image_id)

Edit: What @aneroid wrote is 1000% the right answer and super helpful. You should upvote it. That said, after understanding all that - I went with the BS4 answer because it does the entire job in two lines exactly how I need it to 😂. If you don't actually care about the namespaces it seems waaaaaaay easier.

回答1:

ET.findall() vs BS4.find_all():

• ElementTree's findall() is not recursive by default^*. It's only going to find direct children of the node provided. So in your case, it's only searching for image nodes directly under the root element.
  • ^* as per mzjn's comment below, prefixing the match argument (tag or path) with ".//" will search for that node anywhere in the tree, since it's supports XPath's.
• BeautifulSoup's find_all() searches all descendants. So it seaches for 'imagedata' nodes anywhere in the tree.

• However, ElementTree.iter() does search all descendants. Using the 'working with namespaces' example in the docs:

  >>> for char in root.iter('{http://characters.example.com}character'):
  ...     print(' |-->', char.text)
  ...
   |--> Lancelot
   |--> Archie Leach
   |--> Sir Robin
   |--> Gunther
   |--> Commander Clement
  

• Sadly, ET.iterfind() which works with namespaces as a dict (like ET.findall), also does not search descendants, only direct children by default^*. Just like ET.findall. Apart from how empty strings '' in the tags are treated wrt the namespace, and one returns a list while the other returns an iterator, I can't say there's a meaningful difference between ET.findall and ET.iterfind.
  • ^* As above for ET.findall(), prefixing ".//" makes it search the entire tree (matches with any node).

---

When you use the namespaces with ET, you still need the namespace name with the tag. The results line should be:

namespace = {'v': "urn:schemas-microsoft-com:vml"}
results = ET.fromstring(xml).findall("v:imagedata", namespace)  # note the 'v:'

Also, the 'v' doesn't need to be a 'v', you could change it to something more meaningful if needed:

namespace = {'image': "urn:schemas-microsoft-com:vml"}
results = ET.fromstring(xml).findall("image:imagedata", namespace)

Of course, this still won't necessarily get you all the imagedata elements if they aren't direct children of the root. For that, you'd need to create a recursive function to do it for you. See this answer on SO for how. Note, while that answer does a recursive search, you are likely to hit Python's recursion limit if the descendant depth is too...deep.

To get all the imagedata elements anywhere in the tree, use the ".//" prefix:

results = ET.fromstring(xml).findall(".//v:imagedata", namespace)

回答2:

I'm going to leave the question open, but the workaround I'm currently using is to use BeautifulSoup which happily accepts the v: syntax.

soup = BeautifulSoup(xml, "lxml")

results = soup.find_all("v:imagedata")

回答3:

With ElementTree in Python 3.8, you can simply use a wildcard ({*}) for the namespace:

results = ET.fromstring(xml).findall(".//{*}imagedata") 

Note the .// part, which means that the whole document (all descendants) is searched.

来源：https://stackoverflow.com/questions/62110439/how-to-use-python-xml-findall-to-find-vimagedata-rid-rid7-otitle-1-ren