You are here: Home ‣ Dive Into Python 3 ‣
Difficulty level: ♦♦♦♢♢
❝ FIXME ❞
— FIXME
Most of the chapters in this book have centered around a piece of sample code. But XML isn’t about code; it’s about data. One common use of XML is “syndication feeds” that list the latest articles on a blog, forum, or other frequently-updated website. Most popular blogging software can produce a feed and update it whenever new articles, discussion threads, or blog posts are published. You can follow a blog by “subscribing” to its feed, and you can follow multiple blogs with a dedicated “feed aggregator” like Google Reader.
Here, then, is the XML data we’ll be working with in this chapter. It’s a feed — specifically, an Atom syndication feed.
<?xml version="1.0" encoding="utf-8"?>
<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
<title type="text">dive into mark</title>
<subtitle type="text">currently between addictions</subtitle>
<id>tag:diveintomark.org,2001-07-29:/</id>
<updated>2009-03-27T21:56:07Z</updated>
<link rel="alternate" type="text/html" href="http://diveintomark.org/"/>
<link rel="self" href="http://diveintomark.org/feed/" type="application/atom+xml"/>
<entry>
<author>
<name>Mark</name>
<uri>http://diveintomark.org/</uri>
</author>
<title type="html"><![CDATA[Dive into history, 2009 edition]]></title>
<link rel="alternate" type="text/html"
href="http://diveintomark.org/archives/2009/03/27/dive-into-history-2009-edition"/>
<id>tag:diveintomark.org,2009-03-27:/archives/20090327172042</id>
<updated>2009-03-27T21:56:07Z</updated>
<published>2009-03-27T17:20:42Z</published>
<category scheme="http://diveintomark.org" term="diveintopython"/>
<category scheme="http://diveintomark.org" term="docbook"/>
<category scheme="http://diveintomark.org" term="html"/>
<summary type="html">Putting an entire chapter on one page sounds bloated, but
consider this: my longest chapter so far would be 75 printed pages, and it
loads in under 5 seconds. On dialup.</summary>
</entry>
<entry>
<author>
<name>Mark</name>
<uri>http://diveintomark.org/</uri>
</author>
<title type="html"><![CDATA[Accessibility is a harsh mistress]]></title>
<link rel="alternate" type="text/html"
href="http://diveintomark.org/archives/2009/03/21/accessibility-is-a-harsh-mistress"/>
<id>tag:diveintomark.org,2009-03-21:/archives/20090321200928</id>
<updated>2009-03-22T01:05:37Z</updated>
<published>2009-03-21T20:09:28Z</published>
<category scheme="http://diveintomark.org" term="accessibility"/>
<summary type="html">The accessibility orthodoxy does not permit people to
question the value of features that are rarely useful and rarely used.</summary>
</entry>
<entry>
<author>
<name>Mark</name>
<uri>http://diveintomark.org/</uri>
</author>
<title type="html"><![CDATA[A gentle introduction to video encoding,
part 1: container formats]]></title>
<link rel="alternate" type="text/html"
href="http://diveintomark.org/archives/2008/12/18/give-part-1-container-formats"/>
<id>tag:diveintomark.org,2008-12-18:/archives/20081218155422</id>
<updated>2009-01-11T19:39:22Z</updated>
<published>2008-12-18T15:54:22Z</published>
<category scheme="http://diveintomark.org" term="asf"/>
<category scheme="http://diveintomark.org" term="avi"/>
<category scheme="http://diveintomark.org" term="encoding"/>
<category scheme="http://diveintomark.org" term="flv"/>
<category scheme="http://diveintomark.org" term="GIVE"/>
<category scheme="http://diveintomark.org" term="mp4"/>
<category scheme="http://diveintomark.org" term="ogg"/>
<category scheme="http://diveintomark.org" term="video"/>
<summary type="html">These notes will eventually become part of a
tech talk on video encoding.</summary>
</entry>
</feed>FIXME
FIXME
>>> import xml.etree.ElementTree as etree
>>> tree = etree.parse("examples/feed.xml")
>>> root = tree.getroot()
>>> root
<Element {http://www.w3.org/2005/Atom}feed at cd1eb0>
FIXME
>>> root.tag
'{http://www.w3.org/2005/Atom}feed'
>>> len(root)
9
>>> for child in root:
... print(child)
...
<Element {http://www.w3.org/2005/Atom}title at e2b5d0>
<Element {http://www.w3.org/2005/Atom}subtitle at e2b4e0>
<Element {http://www.w3.org/2005/Atom}id at e2b6c0>
<Element {http://www.w3.org/2005/Atom}updated at e2b6f0>
<Element {http://www.w3.org/2005/Atom}link at e181b0>
<Element {http://www.w3.org/2005/Atom}link at e2b4b0>
<Element {http://www.w3.org/2005/Atom}entry at e2b720>
<Element {http://www.w3.org/2005/Atom}entry at e2b510>
<Element {http://www.w3.org/2005/Atom}entry at e2b750>
FIXME
>>> root.attrib
{'{http://www.w3.org/XML/1998/namespace}lang': 'en'}
>>> root[4]
<Element {http://www.w3.org/2005/Atom}link at e181b0>
>>> root[4].attrib
{'href': 'http://diveintomark.org/', 'type': 'text/html', 'rel': 'alternate'}
>>> root[3]
<Element {http://www.w3.org/2005/Atom}updated at e2b4e0>
>>> root[3].attrib
{}
FIXME
>>> tree.findall("{http://www.w3.org/2005/Atom}entry")
[<Element {http://www.w3.org/2005/Atom}entry at e2b4e0>, <Element {http://www.w3.org/2005/Atom}entry at e2b510>, <Element {http://www.w3.org/2005/Atom}entry at e2b540>]
>>> feed_links = tree.findall("{http://www.w3.org/2005/Atom}link")
>>> feed_links
[<Element {http://www.w3.org/2005/Atom}link at e181b0>, <Element {http://www.w3.org/2005/Atom}link at e2b4b0>]
>>> feed_links[0].attrib
{'href': 'http://diveintomark.org/', 'type': 'text/html', 'rel': 'alternate'}
>>> feed_links[1].attrib
{'href': 'http://diveintomark.org/feed/', 'type': 'application/atom+xml', 'rel': 'self'}
>>> all_links = tree.findall("//{http://www.w3.org/2005/Atom}link")
>>> all_links
[<Element {http://www.w3.org/2005/Atom}link at e181b0>, <Element {http://www.w3.org/2005/Atom}link at e2b4b0>, <Element {http://www.w3.org/2005/Atom}link at e2b570>, <Element {http://www.w3.org/2005/Atom}link at e2b480>, <Element {http://www.w3.org/2005/Atom}link at e2b5a0>]
>>> all_links[0].attrib
{'href': 'http://diveintomark.org/', 'type': 'text/html', 'rel': 'alternate'}
>>> all_links[1].attrib
{'href': 'http://diveintomark.org/feed/', 'type': 'application/atom+xml', 'rel': 'self'}
>>> all_links[2].attrib
{'href': 'http://diveintomark.org/archives/2009/03/27/dive-into-history-2009-edition', 'type': 'text/html', 'rel': 'alternate'}
>>> all_links[3].attrib
{'href': 'http://diveintomark.org/archives/2009/03/21/accessibility-is-a-harsh-mistress', 'type': 'text/html', 'rel': 'alternate'}
>>> all_links[4].attrib
{'href': 'http://diveintomark.org/archives/2008/12/18/give-part-1-container-formats', 'type': 'text/html', 'rel': 'alternate'}
FIXME
>>> from lxml import etree
.
. FIXME (show how it's a drop-in replacement for everything we've done so far)
.
from here on out, use lxml.etree explicitly because these functions are specific to lxml
>>> import lxml.etree
>>> nsmap = {"atom": "http://www.w3.org/2005/Atom"}
>>> tree = lxml.etree.parse("examples/feed.xml")
>>> entries = tree.xpath("//atom:category[@term='accessibility']/..", namespaces=nsmap)
>>> entries
[<Element {http://www.w3.org/2005/Atom}entry at e2b630>]
>>> entry = entries[0]
>>> entry.xpath("./atom:title/text()", namespaces=nsmap)
['Accessibility is a harsh mistress']
FIXME
>>> import lxml.etree
>>> parser = lxml.etree.XMLParser(no_network=True, ns_clean=True, recover=True, remove_blank_text=True, remove_comments=True)
>>> tree = lxml.etree.parse("examples/feed.xml", parser)
FIXME
FIXME
>>> import lxml.etree
>>> new_feed = lxml.etree.Element("{http://www.w3.org/2005/Atom}feed", attrib={"{http://www.w3.org/XML/1998/namespace}lang": "en"})
>>> print(lxml.etree.tounicode(new_feed))
<ns0:feed xmlns:ns0="http://www.w3.org/2005/Atom" xml:lang="en"/>
FIXME
>>> import lxml.etree
>>> new_feed = lxml.etree.Element("feed", nsmap=NSMAP)
>>> print(lxml.etree.tounicode(new_feed))
<feed xmlns="http://www.w3.org/2005/Atom"/>
>>> new_feed.set("{http://www.w3.org/XML/1998/namespace}lang", "en")
>>> print(lxml.etree.tounicode(new_feed))
<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en"/>
FIXME
>>> title = lxml.etree.SubElement(new_feed, "title", attrib={"type":"html"})
>>> print(lxml.etree.tounicode(new_feed))
<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en"><title type="html"/></feed>
>>> title.text = "dive into mark"
>>> print(lxml.etree.tounicode(new_feed))
<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en"><title type="html">dive into mark</title></feed>
>>> print(lxml.etree.tounicode(new_feed, pretty_print=True))
<feed xmlns="http://www.w3.org/2005/Atom" xml:lang="en">
<title type="html">dive into mark</title>
</feed>
© 2001–9 Mark Pilgrim