How can I get specific elements from XML data?

Question

I have some code to retrieve XML data:

import cStringIO
import pycurl
from xml.etree import ElementTree

_API_KEY = 'my api key'
_ima = '/the/path/to/a/image'

sock = cStringIO.StringIO()

upl = pycurl.Curl()

values = [
            ("key", _API_KEY),
            ("image", (upl.FORM_FILE, _ima))]

upl.setopt(upl.URL, "http://api.imgur.com/2/upload.xml")
upl.setopt(upl.HTTPPOST, values)
upl.setopt(upl.WRITEFUNCTION, sock.write)
upl.perform()
upl.close()
xmldata = sock.getvalue()
#print xmldata
sock.close()

The resulting data looks like:

<?xml version="1.0" encoding="utf-8"?>
<upload><image><name></name><title></title><caption></caption><hash>dxPGi</hash><deletehash>kj2XOt4DC13juUW</deletehash><datetime>2011-06-10 02:59:26</datetime><type>image/png</type><animated>false</animated><width>1024</width><height>768</height><size>172863</size><views>0</views><bandwidth>0</bandwidth></image><links><original>http://i.stack.imgur.com/dxPGi.png</original><imgur_page>http://imgur.com/dxPGi</imgur_page><delete_page>http://imgur.com/delete/kj2XOt4DC13juUW</delete_page><small_square>http://i.stack.imgur.com/dxPGis.jpg</small_square><large_thumbnail>http://i.stack.imgur.com/dxPGil.jpg</large_thumbnail></links></upload>

Now, following this answer, I’m trying to get some specific values from the data.

This is my attempt:

tree = ElementTree.fromstring(xmldata)
url = tree.findtext('original')
webpage = tree.findtext('imgur_page')
delpage = tree.findtext('delete_page')

print 'Url: ' + str(url)
print 'Pagina: ' + str(webpage)
print 'Link de borrado: ' + str(delpage)

I get an AttributeError if I try to add the .text access:

Traceback (most recent call last):
  File "<pyshell#28>", line 27, in <module>
    url = tree.find('original').text
AttributeError: 'NoneType' object has no attribute 'text'

I couldn’t find anything in Python’s help for ElementTree about this attribute. How can I get only the text, not the object?

I found some info about getting a text string here; but when I try it I get a TypeError:

Traceback (most recent call last): 
  File "<pyshell#32>", line 34, in <module>
    print 'Url: ' + url
TypeError: cannot concatenate 'str' and 'NoneType' objects

If I try to print 'Url: ' + str(url) instead, there is no error, but the result shows as None.

How can I get the url, webpageanddelete_page` data from this XML?

Asked By: Braiam

||

Source

Answer 1

Your find() call is trying to find an immediate child of the top of the tree with a tag named original, not a tag at any lower level than that. Use:

url = tree.find('.//original').text

if you want to find all elements in the tree with the tag named original. The pattern matching rules for ElementTree’s find() method are laid out in a table on this page: http://effbot.org/zone/element-xpath.htm

For // matching it says:

Selects all subelements, on all levels beneath the current element (search the entire subtree). For example, “.//egg” selects all “egg” elements in the entire tree.

Edit: here is some test code for you, it use the XML sample string you posted I just ran it through XML Tidy in TextMate to make it legible:

from xml.etree import ElementTree
xmldata = '''<?xml version="1.0" encoding="utf-8"?>
<upload>
    <image>
        <name/>
        <title/>
        <caption/>
        <hash>dxPGi</hash>
        <deletehash>kj2XOt4DC13juUW</deletehash>
        <datetime>2011-06-10 02:59:26</datetime>
        <type>image/png</type>
        <animated>false</animated>
        <width>1024</width>
        <height>768</height>
        <size>172863</size>
        <views>0</views>
        <bandwidth>0</bandwidth>
</image>
<links>
    <original>http://i.stack.imgur.com/dxPGi.png</original>
    <imgur_page>http://imgur.com/dxPGi</imgur_page>
    <delete_page>http://imgur.com/delete/kj2XOt4DC13juUW</delete_page>
    <small_square>http://i.stack.imgur.com/dxPGis.jpg</small_square>
    <large_thumbnail>http://i.stack.imgur.com/dxPGil.jpg</large_thumbnail>
</links>
</upload>'''
tree = ElementTree.fromstring(xmldata)
print tree.find('.//original').text

On my machine (OS X running python 2.6.1) that produces:

Ian-Cs-MacBook-Pro:tmp ian$ python test.py 
http://i.stack.imgur.com/dxPGi.png

Answered By: Ian C.

How can I get specific elements from XML data?

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