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Worksheet 15.2 Parsing XML
Look at the code below and predict what will be printed.
Here is a simple application that parses some XML and extracts some data elements from the XML:
Activity 15.2.2.
Run this to see what it prints.
The triple single quote (
'''), as well as the triple double quote ("""), allow for the creation of strings in Python that span multiple lines.
Calling
fromstring converts the string representation of the XML into a “tree” of XML elements. When the XML is in a tree, we have a series of methods we can call to extract portions of data from the XML string. The find function searches through the XML tree and retrieves the element that matches the specified tag. The get gets the value of the attribute in that tag.
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.
Using get to get the value of an attribute
Why do we use
get to get the value of an attribute?
Look at the code below and predict what will be printed.
Note 15.2.1.
Just like with dictionaries we can use
get to get the value of an attribute and if the attribute isn’t there the default is to return None.
Getting Data from the First Element of a Type in XML
You can use
find to get the first element of the XML of a specified type. You can the use find on that element to get children tags of that element.
What do you think would happen if we looked for the first ‘author’ in
tree rather than in book? Modify the code to see what happens.
Fixing Errors in XML
If your XML has errors, what do you think will happen?
Write Code to Process XML
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