How can I convert XML into a Python object?

Question

I need to load an XML file and convert the contents into an object-oriented Python structure. I want to take this:

Answer 1

There are three common XML parsers for python: xml.dom.minidom, elementree, and BeautifulSoup.

IMO, BeautifulSoup is by far the best.

http://www.crummy.com/software/BeautifulSoup/

Answer 2

How about this

http://evanjones.ca/software/simplexmlparse.html

Answer 3

It's worth looking at lxml.objectify.

xml = """<main>
<object1 attr="name">content</object1>
<object1 attr="foo">contenbar</object1>
<test>me</test>
</main>"""

from lxml import objectify

main = objectify.fromstring(xml)
main.object1[0]             # content
main.object1[1]             # contenbar
main.object1[0].get("attr") # name
main.test                   # me

Or the other way around to build xml structures:

item = objectify.Element("item")
item.title = "Best of python"
item.price = 17.98
item.price.set("currency", "EUR")

order = objectify.Element("order")
order.append(item)
order.item.quantity = 3
order.price = sum(item.price * item.quantity for item in order.item)

import lxml.etree
print(lxml.etree.tostring(order, pretty_print=True))

Output:

<order>
  <item>
    <title>Best of python</title>
    <price currency="EUR">17.98</price>
    <quantity>3</quantity>
  </item>
  <price>53.94</price>
</order>

Answer 4

David Mertz's gnosis.xml.objectify would seem to do this for you. Documentation's a bit hard to come by, but there are a few IBM articles on it, including this one (text only version).

from gnosis.xml import objectify

xml = "<root><nodes><node>node 1</node><node>node 2</node></nodes></root>"
root = objectify.make_instance(xml)

print root.nodes.node[0].PCDATA # node 1
print root.nodes.node[1].PCDATA # node 2

Creating xml from objects in this way is a different matter, though.

Answer 5

#@Stephen: 
#"can't hardcode the element names, so I need to collect them 
#at parse and use them somehow as the object names."

#I don't think thats possible. Instead you can do this. 
#this will help you getting any object with a required name.

import BeautifulSoup


class Coll(object):
    """A class which can hold your Foo clas objects 
    and retrieve them easily when you want
    abstracting the storage and retrieval logic
    """
    def __init__(self):
        self.foos={}        

    def add(self, fooobj):
        self.foos[fooobj.name]=fooobj

    def get(self, name):
        return self.foos[name]

class Foo(object):
    """The required class
    """
    def __init__(self, name, attr1=None, attr2=None):
        self.name=name
        self.attr1=attr1
        self.attr2=attr2

s="""<main>
         <object name="somename">
             <attr name="attr1">value1</attr>
             <attr name="attr2">value2</attr>
         </object>
         <object name="someothername">
             <attr name="attr1">value3</attr>
             <attr name="attr2">value4</attr>
         </object>
     </main>
"""

#

soup=BeautifulSoup.BeautifulSoup(s)


bars=Coll()
for each in soup.findAll('object'):
    bar=Foo(each['name'])
    attrs=each.findAll('attr')
    for attr in attrs:
        setattr(bar, attr['name'], attr.renderContents())
    bars.add(bar)


#retrieve objects by name
print bars.get('somename').__dict__

print '\n\n', bars.get('someothername').__dict__

output

{'attr2': 'value2', 'name': u'somename', 'attr1': 'value1'}


{'attr2': 'value4', 'name': u'someothername', 'attr1': 'value3'}

Answer 6

If googling around for a code-generator doesn't work, you could write your own that uses XML as input and outputs objects in your language of choice.

It's not terribly difficult, however the three step process of Parse XML, Generate Code, Compile/Execute Script does making debugging a bit harder.