13.1: eXtensible Markup Language - XML
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XML looks very similar to HTML, but XML is more structured than HTML. Here is a sample of an XML document:
<person> <name>Chuck</name> <phone type="intl"> +1 734 303 4456 </phone> <email hide="yes"/> </person>
Often it is helpful to think of an XML document as a tree structure where there is a top tag
person and other tags such as
phone are drawn as children of their parent nodes.
A Tree Representation of XML
Here is a simple application that parses some XML and extracts some data elements from the XML:
Code 13.1.1 (Python)
%%python3 import xml.etree.ElementTree as ET data = ''' <person> <name>Chuck</name> <phone type=\"intl\"> +1 734 303 4456 </phone> <email hide=\"yes\"/> </person>''' tree = ET.fromstring(data) print('Name:', tree.find('name').text) print('Attr:', tree.find('email').get('hide')) # Code: http://www.py4e.com/code3/xml1.py
fromstring converts the string representation of the XML into a "tree" of XML nodes. When the XML is in a tree, we have a series of methods we can call to extract portions of data from the XML.
find function searches through the XML tree and retrieves a node that matches the specified tag. Each node can have some text, some attributes (like hide), and some "child" nodes. Each node can be the top of a tree of nodes.
Name: Chuck Attr: yes
Using an XML parser such as
ElementTree has the advantage that while the XML in this example is quite simple, it turns out there are many rules regarding valid XML and using
ElementTree allows us to extract data from XML without worrying about the rules of XML syntax.