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books.xml
<?xml version="1.0"?>
<catalog>
    <book id="bk101">
        <author>Gambardella, Matthew</author>
        <title>XML Developer's Guide</title>
        <genre>Computer</genre>
        <price>44.95</price>
        <publish_date>2000-10-01</publish_date>
        <description>An in-depth look at creating applications 
        with XML.</description>
    </book>
    <book id="bk102">
        <author>Ralls, Kim</author>
        <title>Midnight Rain</title>
        <genre>Fantasy</genre>
        <price>5.95</price>
        <publish_date>2000-12-16</publish_date>
        <description>A former architect battles corporate zombies, 
        an evil sorceress, and her own childhood to become queen 
        of the world.</description>
    </book>
    <book id="bk103">
        <author>Corets, Eva</author>
        <title>Maeve Ascendant</title>
        <genre>Fantasy</genre>
        <price>5.95</price>
        <publish_date>2000-11-17</publish_date>
        <description>After the collapse of a nanotechnology 
        society in England, the young survivors lay the 
        foundation for a new society.</description>
    </book>
    <book id="bk104">
        <author>Corets, Eva</author>
        <title>Oberon's Legacy</title>
        <genre>Fantasy</genre>
        <price>5.95</price>
        <publish_date>2001-03-10</publish_date>
        <description>In post-apocalypse England, the mysterious 
        agent known only as Oberon helps to create a new life 
        for the inhabitants of London. Sequel to Maeve 
        Ascendant.</description>
    </book>
    <book id="bk105">
        <author>Corets, Eva</author>
        <title>The Sundered Grail</title>
        <genre>Fantasy</genre>
        <price>5.95</price>
        <publish_date>2001-09-10</publish_date>
        <description>The two daughters of Maeve, half-sisters, 
        battle one another for control of England. Sequel to 
        Oberon's Legacy.</description>
    </book>
    <book id="bk106">
        <author>Randall, Cynthia</author>
        <title>Lover Birds</title>
        <genre>Romance</genre>
        <price>4.95</price>
        <publish_date>2000-09-02</publish_date>
        <description>When Carla meets Paul at an ornithology 
        conference, tempers fly as feathers get ruffled.</description>
    </book>
    <book id="bk107">
        <author>Thurman, Paula</author>
        <title>Splish Splash</title>
        <genre>Romance</genre>
        <price>4.95</price>
        <publish_date>2000-11-02</publish_date>
        <description>A deep sea diver finds true love twenty 
        thousand leagues beneath the sea.</description>
    </book>
    <book id="bk108">
        <author>Knorr, Stefan</author>
        <title>Creepy Crawlies</title>
        <genre>Horror</genre>
        <price>4.95</price>
        <publish_date>2000-12-06</publish_date>
        <description>An anthology of horror stories about roaches,
        centipedes, scorpions  and other insects.</description>
    </book>
    <book id="bk109">
        <author>Kress, Peter</author>
        <title>Paradox Lost</title>
        <genre>Science Fiction</genre>
        <price>6.95</price>
        <publish_date>2000-11-02</publish_date>
        <description>After an inadvertant trip through a Heisenberg
        Uncertainty Device, James Salway discovers the problems 
        of being quantum.</description>
    </book>
    <book id="bk110">
        <author>O'Brien, Tim</author>
        <title>Microsoft .NET: The Programming Bible</title>
        <genre>Computer</genre>
        <price>36.95</price>
        <publish_date>2000-12-09</publish_date>
        <description>Microsoft's .NET initiative is explored in 
        detail in this deep programmer's reference.</description>
    </book>
    <book id="bk111">
        <author>O'Brien, Tim</author>
        <title>MSXML3: A Comprehensive Guide</title>
        <genre>Computer</genre>
        <price>36.95</price>
        <publish_date>2000-12-01</publish_date>
        <description>The Microsoft MSXML3 parser is covered in 
        detail, with attention to XML DOM interfaces, XSLT processing, 
        SAX and more.</description>
    </book>
    <book id="bk112">
        <author>Galos, Mike</author>
        <title>Visual Studio 7: A Comprehensive Guide</title>
        <genre>Computer</genre>
        <price>49.95</price>
        <publish_date>2001-04-16</publish_date>
        <description>Microsoft Visual Studio 7 is explored in depth,
        looking at how Visual Basic, Visual C++, C#, and ASP+ are 
        integrated into a comprehensive development 
        environment.</description>
    </book>
</catalog>

The etree submodule contains the ElementTree object which can open a string filename to deserialize XML data using parse(), which returns an ElementTree object, representing an XML document. A Python string can also be parsed with fromstring(), which actually returns an Element object.

tree = xml.etree.ElementTree.parse('books.xml')
tree = xml.etree.ElementTree.fromstring(books)

The getroot() method returns an Element object of the XML document's root node.

root = tree.getroot()

The parsed data can be displayed using the tostring() static method, providing an Element as argument.

ElementTree.tostring(root)

Children of an element can be filtered using findall(). This returns a list of Elements.

books = root.findall('book')

Any Element object exposes an attrib property which returns a dictionary of attributes.

[b.attrib for b in books]

Attributes can be written to an Element using the set() method.

root.set('foo','bar')

Attributes can also be manipulated on the attrib property with normal Python dictionary operations.

root.attrib['foo'] = 'bar'
del(root.attrib['hello'])

Commit changes to disk. The argument can be a string representing the filename or a file object (in which case the file must be opened as a binary). Encoding can be specified (default is UTF-8) and a XML declaration can also be automatically generated.

tree.write('books.xml', encoding='UTF-16', xml_declaration=True)
with open('books.xml', 'wb') as f:
    tree.write(f)

Find elements by element name

tree.findall('book')