A generic script using expat to convert xml into objects
Python, 92 lines
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Borrowed from wxPython XML tree demo and modified.
"""
import string
from xml.parsers import expat
class Element:
'A parsed XML element'
def __init__(self,name,attributes):
'Element constructor'
# The element's tag name
self.name = name
# The element's attribute dictionary
self.attributes = attributes
# The element's cdata
self.cdata = ''
# The element's child element list (sequence)
self.children = []
def AddChild(self,element):
'Add a reference to a child element'
self.children.append(element)
def getAttribute(self,key):
'Get an attribute value'
return self.attributes.get(key)
def getData(self):
'Get the cdata'
return self.cdata
def getElements(self,name=''):
'Get a list of child elements'
#If no tag name is specified, return the all children
if not name:
return self.children
else:
# else return only those children with a matching tag name
elements = []
for element in self.children:
if element.name == name:
elements.append(element)
return elements
class Xml2Obj:
'XML to Object'
def __init__(self):
self.root = None
self.nodeStack = []
def StartElement(self,name,attributes):
'SAX start element even handler'
# Instantiate an Element object
element = Element(name.encode(),attributes)
# Push element onto the stack and make it a child of parent
if len(self.nodeStack) > 0:
parent = self.nodeStack[-1]
parent.AddChild(element)
else:
self.root = element
self.nodeStack.append(element)
def EndElement(self,name):
'SAX end element event handler'
self.nodeStack = self.nodeStack[:-1]
def CharacterData(self,data):
'SAX character data event handler'
if string.strip(data):
data = data.encode()
element = self.nodeStack[-1]
element.cdata += data
return
def Parse(self,filename):
# Create a SAX parser
Parser = expat.ParserCreate()
# SAX event handlers
Parser.StartElementHandler = self.StartElement
Parser.EndElementHandler = self.EndElement
Parser.CharacterDataHandler = self.CharacterData
# Parse the XML File
ParserStatus = Parser.Parse(open(filename,'r').read(), 1)
return self.root
parser = Xml2Obj()
element = parser.Parse('sample.xml')
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I saw Christoph Dietze's script to turn the structure of a XML-document into a combination of dictionaries and lists which is a good idea. xml2obj is a variation of the concept and differs by:
Using expat. The dom parser has a lot of overhead because it creates its own data structures, which were being used to create a second set of structures.
Uses a stack to append child elements to parent.
Uses classes to enhance access to the elements.
Tags: xml
Output. How do you print out the parsed xml object? Do you have any examples? Thanks.
I took this code and updated it to where it works pretty well for me now. First, I changed the Element to have its attributes in a dictionary. Then I added a few methods to provide easy access within the tree. Since I am very new to XML, I borrowed ideas from this recipe and a few notes by Uche Ogbuji. If you are interested, I would be happy to send the code with examples. I have never commented here nor posted any code so I really don't know how to approach it.
obj2xml: and back again. Add this method to Element to recreate the XML:
or you could even call this method __str__ to make it easy.
Has anyone tried it with GML with CDATA sections to extract data out?
What I can see is that it takes in a sample.xml file. I have got a sample.xml file now, but how do I save data into a new file?
Basically, it seems to be a good idea but there is a lack of documentation/instruction on how to use it.