instance_alink = root.find('{http://www.w3.org/2005/Atom}link')

import xml.etree.cElementTree as ET

tree = ET.parse('../../external_data/rss.xml')
root = tree.getroot()

instance_title = root.find('channel/title').text
instance_link = root.find('channel/link').text
instance_alink = root.find('{http://www.w3.org/2005/Atom}link')
instance_description = root.find('channel/description').text
instance_language = root.find('channel/language').text
instance_pubDate = root.find('channel/pubDate').text
instance_lastBuildDate = root.find('channel/lastBuildDate').text

<?xml version="1.0" encoding="windows-1252"?>
<rss version="2.0">
  <channel>
    <title>Filings containing financial statements tagged using the US GAAP or IFRS taxonomies.</title>
    <link>http://www.example.com</link>
    <atom:link href="http://www.example.com" rel="self" type="application/rss+xml" xmlns:atom="http://www.w3.org/2005/Atom"/>
    <description>This is a list of up to 200 of the latest filings containing financial statements tagged using the US GAAP or IFRS taxonomies, updated every 10 minutes.</description>
    <language>en-us</language>
    <pubDate>Mon, 20 Nov 2017 20:20:45 EST</pubDate>
    <lastBuildDate>Mon, 20 Nov 2017 20:20:45 EST</lastBuildDate>
....

<atom:link href="http://www.example.com" rel="self" type="application/rss+xml" xmlns:atom="http://www.w3.org/2005/Atom"/>

instance_alink = root.find('{http://www.w3.org/2005/Atom}link').attrib