Converting Xml to Json Using Python?
I've Seen a Fair Share of Ungainly Xml->Json Code on the Web, and Having Interacted with Stack's Users for a Bit, I'm Convinced That This Crowd Can Help More...
I've seen a fair share of ungainly XML->JSON code on the web, and having interacted with Stack's users for a bit, I'm convinced that this crowd can help more than the first few pages of Google results can.
So, we're parsing a weather feed, and we need to populate weather widgets on a multitude of web sites. We're looking now into Python-based solutions.
This public weather.com RSS feed is a good example of what we'd be parsing (our actual weather.com feed contains additional information because of a partnership w/them).
In a nutshell, how should we convert XML to JSON using Python?
20 Answers
xmltodict (full disclosure: I wrote it) can help you convert your XML to a dict+list+string structure, following this "standard". It is Expat-based, so it's very fast and doesn't need to load the whole XML tree in memory.
Once you have that data structure, you can serialize it to JSON:
import xmltodict, json
o = xmltodict.parse('<e> <a>text</a> <a>text</a> </e>')
json.dumps(o) # '{"e": {"a": ["text", "text"]}}'
There is no "one-to-one" mapping between XML and JSON, so converting one to the other necessarily requires some understanding of what you want to do with the results.
That being said, Python's standard library has several modules for parsing XML (including DOM, SAX, and ElementTree). As of Python 2.6, support for converting Python data structures to and from JSON is included in the json module.
So the infrastructure is there.
You can use the xmljson library to convert using different XML JSON conventions.
For example, this XML:
<p id="1">text</p>
translates via the BadgerFish convention into this:
{
'p': {
'@id': 1,
'$': 'text'
}
}
and via the GData convention into this (attributes are not supported):
{
'p': {
'$t': 'text'
}
}
... and via the Parker convention into this (attributes are not supported):
{
'p': 'text'
}
It's possible to convert from XML to JSON and from JSON to XML using the same conventions:
>>> import json, xmljson
>>> from lxml.etree import fromstring, tostring
>>> xml = fromstring('<p id="1">text</p>')
>>> json.dumps(xmljson.badgerfish.data(xml))
'{"p": {"@id": 1, "$": "text"}}'
>>> xmljson.parker.etree({'ul': {'li': [1, 2]}})
# Creates [<ul><li>1</li><li>2</li></ul>]
Disclosure: I wrote this library. Hope it helps future searchers.
If some time you get only response code instead of all data then error like json parse will be there so u need to convert it as text
import xmltodict
data = requests.get(url)
xpars = xmltodict.parse(data.text)
json = json.dumps(xpars)
print json
To anyone that may still need this. Here's a newer, simple code to do this conversion.
from xml.etree import ElementTree as ET
xml = ET.parse('FILE_NAME.xml')
parsed = parseXmlToJson(xml)
def parseXmlToJson(xml):
response = {}
for child in list(xml):
if len(list(child)) > 0:
response[child.tag] = parseXmlToJson(child)
else:
response[child.tag] = child.text or ''
# one-liner equivalent
# response[child.tag] = parseXmlToJson(child) if len(list(child)) > 0 else child.text or ''
return response
Here's the code I built for that. There's no parsing of the contents, just plain conversion.
from xml.dom import minidom
import simplejson as json
def parse_element(element):
dict_data = dict()
if element.nodeType == element.TEXT_NODE:
dict_data['data'] = element.data
if element.nodeType not in [element.TEXT_NODE, element.DOCUMENT_NODE,
element.DOCUMENT_TYPE_NODE]:
for item in element.attributes.items():
dict_data[item[0]] = item[1]
if element.nodeType not in [element.TEXT_NODE, element.DOCUMENT_TYPE_NODE]:
for child in element.childNodes:
child_name, child_dict = parse_element(child)
if child_name in dict_data:
try:
dict_data[child_name].append(child_dict)
except AttributeError:
dict_data[child_name] = [dict_data[child_name], child_dict]
else:
dict_data[child_name] = child_dict
return element.nodeName, dict_data
if __name__ == '__main__':
dom = minidom.parse('data.xml')
f = open('data.json', 'w')
f.write(json.dumps(parse_element(dom), sort_keys=True, indent=4))
f.close()
There is a method to transport XML-based markup as JSON which allows it to be losslessly converted back to its original form. See .
It's a kind of XSLT of JSON. I hope you find it helpful
You may want to have a look at . This project starts off with an XML to JSON conversion of a large library of XML files. There was much research done in the conversion, and the most simple intuitive XML -> JSON mapping was produced (it is described early in the document). In summary, convert everything to a JSON object, and put repeating blocks as a list of objects.
objects meaning key/value pairs (dictionary in Python, hashmap in Java, object in JavaScript)
There is no mapping back to XML to get an identical document, the reason is, it is unknown whether a key/value pair was an attribute or an <key>value</key>, therefore that information is lost.
If you ask me, attributes are a hack to start; then again they worked well for HTML.
I'd suggest not going for a direct conversion. Convert XML to an object, then from the object to JSON.
In my opinion, this gives a cleaner definition of how the XML and JSON correspond.
It takes time to get right and you may even write tools to help you with generating some of it, but it would look roughly like this:
class Channel:
def __init__(self)
self.items = []
self.title = ""
def from_xml( self, xml_node ):
self.title = xml_node.xpath("title/text()")[0]
for x in xml_node.xpath("item"):
item = Item()
item.from_xml( x )
self.items.append( item )
def to_json( self ):
retval = {}
retval['title'] = title
retval['items'] = []
for x in items:
retval.append( x.to_json() )
return retval
class Item:
def __init__(self):
...
def from_xml( self, xml_node ):
...
def to_json( self ):
...
Well, probably the simplest way is just parse the XML into dictionaries and then serialize that with simplejson.
When I do anything with XML in python I almost always use the lxml package. I suspect that most people use lxml. You could use xmltodict but you will have to pay the penalty of parsing the XML again.
To convert XML to json with lxml you:
- Parse XML document with lxml
- Convert lxml to a dict
- Convert list to json
I use the following class in my projects. Use the toJson method.
from lxml import etree
import json
class Element:
'''
Wrapper on the etree.Element class. Extends functionality to output element
as a dictionary.
'''
def __init__(self, element):
'''
:param: element a normal etree.Element instance
'''
self.element = element
def toDict(self):
'''
Returns the element as a dictionary. This includes all child elements.
'''
rval = {
self.element.tag: {
'attributes': dict(self.element.items()),
},
}
for child in self.element:
rval[self.element.tag].update(Element(child).toDict())
return rval
class XmlDocument:
'''
Wraps lxml to provide:
- cleaner access to some common lxml.etree functions
- converter from XML to dict
- converter from XML to json
'''
def __init__(self, xml = '<empty/>', filename=None):
'''
There are two ways to initialize the XmlDocument contents:
- String
- File
You don't have to initialize the XmlDocument during instantiation
though. You can do it later with the 'set' method. If you choose to
initialize later XmlDocument will be initialized with "<empty/>".
:param: xml Set this argument if you want to parse from a string.
:param: filename Set this argument if you want to parse from a file.
'''
self.set(xml, filename)
def set(self, xml=None, filename=None):
'''
Use this to set or reset the contents of the XmlDocument.
:param: xml Set this argument if you want to parse from a string.
:param: filename Set this argument if you want to parse from a file.
'''
if filename is not None:
self.tree = etree.parse(filename)
self.root = self.tree.getroot()
else:
self.root = etree.fromstring(xml)
self.tree = etree.ElementTree(self.root)
def dump(self):
etree.dump(self.root)
def getXml(self):
'''
return document as a string
'''
return etree.tostring(self.root)
def xpath(self, xpath):
'''
Return elements that match the given xpath.
:param: xpath
'''
return self.tree.xpath(xpath);
def nodes(self):
'''
Return all elements
'''
return self.root.iter('*')
def toDict(self):
'''
Convert to a python dictionary
'''
return Element(self.root).toDict()
def toJson(self, indent=None):
'''
Convert to JSON
'''
return json.dumps(self.toDict(), indent=indent)
if __name__ == "__main__":
xml='''<system>
<product>
<demod>
<frequency value='2.215' units='MHz'>
<blah value='1'/>
</frequency>
</demod>
</product>
</system>
'''
doc = XmlDocument(xml)
print doc.toJson(indent=4)
The output from the built in main is:
{
"system": {
"attributes": {},
"product": {
"attributes": {},
"demod": {
"attributes": {},
"frequency": {
"attributes": {
"units": "MHz",
"value": "2.215"
},
"blah": {
"attributes": {
"value": "1"
}
}
}
}
}
}
}
Which is a transformation of this xml:
<system>
<product>
<demod>
<frequency value='2.215' units='MHz'>
<blah value='1'/>
</frequency>
</demod>
</product>
</system>
I found for simple XML snips, use regular expression would save troubles. For example:
# <user><name>Happy Man</name>...</user>
import re
names = re.findall(r'<name>(\w+)<\/name>', xml_string)
# do some thing to names
To do it by XML parsing, as @Dan said, there is not one-for-all solution because the data is different. My suggestion is to use lxml. Although not finished to json, lxml.objectify give quiet good results:
>>> from lxml import objectify
>>> root = objectify.fromstring("""
... <root xmlns:xsi="">
... <a attr1="foo" attr2="bar">1</a>
... <a>1.2</a>
... <b>1</b>
... <b>true</b>
... <c>what?</c>
... <d xsi:nil="true"/>
... </root>
... """)
>>> print(str(root))
root = None [ObjectifiedElement]
a = 1 [IntElement]
* attr1 = 'foo'
* attr2 = 'bar'
a = 1.2 [FloatElement]
b = 1 [IntElement]
b = True [BoolElement]
c = 'what?' [StringElement]
d = None [NoneElement]
* xsi:nil = 'true'
While the built-in libs for XML parsing are quite good I am partial to lxml.
But for parsing RSS feeds, I'd recommend Universal Feed Parser, which can also parse Atom. Its main advantage is that it can digest even most malformed feeds.
Python 2.6 already includes a JSON parser, but a newer version with improved speed is available as simplejson.
With these tools building your app shouldn't be that difficult.
My answer addresses the specific (and somewhat common) case where you don't really need to convert the entire xml to json, but what you need is to traverse/access specific parts of the xml, and you need it to be fast, and simple (using json/dict-like operations).
Must Read
Approach
For this, it is important to note that parsing an xml to etree using lxml is super fast. The slow part in most of the other answers is the second pass: traversing the etree structure (usually in python-land), converting it to json.
Which leads me to the approach I found best for this case: parsing the xml using lxml, and then wrapping the etree nodes (lazily), providing them with a dict-like interface.