So I will ask the question somewhat vaugley because I'm first not sure if the question can be asked.. Here goes,
I want to read an XML tree in using Python3 which I am new to. I have accomplished this with relative ease using:
xml.etree.ElementTree.parse(urllib.request.urlopen(url))
The XML stream are different data sets and there is a XSD which is available which I have also parsed int he same way. Now, my question is can I create a parser using the XSD schema? I am new to XML in this way, but I have found examples where the parser object was generated using the XSD then the XML was read in accordingly. However, I cannot find the equivalent in Python3.
Here is vaugely what I want in Python2.X:
schema = etree.XMLSchema(schema_root)
xmlparser = etree.XMLParser(schema=schema)
I'm not sure if I'm even conceptualizing this correctly. Maybe this is an XML problem not a python problem, i.e., maybe you can only validate the XML against the schema and not actually use it to parse with the specifics from the XSD. Anyone help clear this up?
xmlschema is a Python module to manage XML Schemas or validate XML instances to the XSD.
Example to validate XML documents from URL against the XML Schema using Python3.
import requests
import xmlschema
import xml.etree.ElementTree as ET
# to make it simple use external XML Schema and create a local file from it to validate XML examples
xsd_url = "https://raw.githubusercontent.com/sissaschool/xmlschema/master/tests/test_cases/examples/collection/collection.xsd"
with open("test.xsd", "w", newline="") as out:
out.write(requests.get(xsd_url).text)
xsd = xmlschema.XMLSchema("test.xsd")
# XML #1 validates to the Schema
url1 = "https://raw.githubusercontent.com/sissaschool/xmlschema/master/tests/test_cases/examples/collection/collection.xml"
xt = ET.fromstring(requests.get(url1).text)
print("xml1 valid=", xsd.is_valid(xt), sep="")
# XML #2 with invalid structure
url2 = "https://raw.githubusercontent.com/sissaschool/xmlschema/master/tests/test_cases/examples/collection/collection-1_error.xml"
xt = ET.fromstring(requests.get(url2).text)
print("xml2 valid=", xsd.is_valid(xt), sep="")
Output:
xml1 valid=True
xml2 valid=False
Related
I have multiple XSD strings in my Python program, for example.
xsd1 = '''<?xml version...
<xs:schema targetNamespace="...
'''
xsd2 = '''...'''
import xmlschema
schema = xmlschema.XMLSchema([xsd1, xsd2]) # it seems xmlschema does not accept such arguments
# then using schema to validate xml files
The two XSD have different target name spaces. How can I read them into xmlschema and validate xml files?
Ideally the xmlschema.XMLSchema() constructor would accept a list of file locations and assemble a single XSD model from them all (Eclipse EMF XSD model can do this). But it looks as if xmlschema does not do that trick.
The workaround is to create a single wrapper XSD that imports/includes the other XSDs, and then give the wrapper XSD to xmlschema.
I have a problem, where I want to change some lines in my XML, but this XML is not in file, it is in string. I am using Python 3.x and lib xml.etree.ElementTree for this purpose.
I have these piece of code which I know works for files in project, but as I said, I want no files, only operations on string sources.
source_tree = ET.ElementTree(ET.fromstring(source_config))
source_tree_root = ET.fromstring(source_config)
for item in source_tree_root.iter('generation'):
item.text = item.text.replace(self.firstarg, self.secondarg)
This works, but I don't know how to save it. I tried
source_tree.write(source_config, encoding='latin-1') but this doesn't work (treats all XML as a name).
I don't think you need both source_tree and source_tree_root. By having both, you're creating two separate things. When you write using source_tree, you don't get the changes made to source_tree_root.
Try creating an ElementTree from source_tree_root (which is just an Element), like this (untested since you didn't supply an mcve)...
source_tree_root = ET.fromstring(source_config)
for item in source_tree_root.iter('generation'):
item.text = item.text.replace(self.firstarg, self.secondarg)
ET.ElementTree(source_tree_root).write("output.xml")
OK, I thought that you were using lxml. My bad. Well here is how you would do it with lxml. I think that lxml is superior.
Here is the basic way of parsing a string into an XML document.
from lxml import etree
doc = etree.fromstring(yourstring)
for e in doc.xpath('//sometagname'):
e.set('foo', 'bar')
I'm trying to create a face-detection script using Python's OpenCV using the haar cascade XML file.
My goal is to upload a python file to a website but due to some weird policies, I can only upload the Python file, without the XML...
The question is, is it possible to somehow put the XML file inside the Python script, say, convert it to a String or something and then generate an XML from that String?
xml = """<?xml version="1.0" encoding="UTF-8"?>
<a>
<b>Yes, you can embed XML in a string literal in Python.</b>
</a>"""
Not answer to title but answer of your description question.
Haar cascade doesn't support non-file XML strings. Also, if you try to put an XML file to a website and give a link to an XML file with cv2.CascadeClassifier(), it will give an error.
But you can use the request module on python to achieve what you want.
It gets XML from the website, then puts it into a file
def function(self, image):
# download XML from server
link = LINK_TO_XML
r = requests.get(link, allow_redirects=True)
open('haarcascade_frontalface_default.xml', 'wb').write(r.content)
# end of download
haar_cascade = cv.CascadeClassifier('haarcascade_frontalface_default.xml')
First, copy the contents of the XML file into the python file and assign the whole thing to a string. Then use XML library to create a tree type data structure named root which contains the contents of the XML file. This tree is traversable and you can do what you like with it in your program:
import xml.etree.ElementTree as ET
root = ET.fromstring(XML_file_example_as_string).
To generate XML from the string you can use ElementTree.write() like this:
tree = ET.ElementTree(root)
tree.write('example.xml')
So, my problem is I'm trying to do something a little un-orthodox. I have a complicated set of XSD files. However I don't want to use these XSD files to verify an XML file; I want to parse these XSDs as XML and interrogate them just as I would a normal XML file. This is possible because XSDs are valid XML. I am using lxml with Python3.
The problem I'm having is with the statement:
<xs:include schemaLocation="sdm-extension.xsd"/>
If I instruct lxml to create an XSD for verifying like this:
schema = etree.XMLSchema(schema_root)
this dependency will be resolved (the file exists in the same directory as the one I've just loaded). HOWEVER, I am treating these as XML so, correctly, lxml just treats this as a normal element with an attribute and does not follow it.
Is there an easy or correct way to extend lxml so that I may have the same or similar behaviour as, say
<xi:include href="metadata.xml" parse="xml" xpointer="title"/>
I could, of course, create a separate xml file manually that includes all the dependencies in the XSD schema. That is perhaps a solution?
So it seems like one option is to use the xi:xinclude method and create a separate xml file that includes all the XSDs I want to parse. Something along the lines of:
<fullxsd>
<xi:include href="./xsd-cdisc-sdm-1.0.0/sdm1-0-0.xsd" parse="xml"/>
<xi:include href="./xsd-cdisc-sdm-1.0.0/sdm-ns-structure.xsd" parse="xml"/>
</fullxsd>
Then use some lxml along the lines of
def combine(xsd_file):
with open(xsd_file, 'rb') as f_xsd:
parser = etree.XMLParser(recover=True, encoding='utf-8',remove_comments=True, remove_blank_text=True)
xsd_source = f_xsd.read()
root = etree.fromstring(xsd_source, parser)
incl = etree.XInclude()
incl(root)
print(etree.tostring(root, pretty_print=True))
Its not ideal but it seems the proper way. I've looked at custom URI parsers in the lxml but that would mean actually altering the XSDs which seems messier.
Try this:
def validate_xml(schema_file, xml_file):
xsd_doc = etree.parse(schema_file)
xsd = etree.XMLSchema(xsd_doc)
xml = etree.parse(xml_file)
return xsd.validate(xml)
Is there a way to read an XML document in Python without the schema? In my use case there is a file similar to the following.
<people>
<human>
<weight>75</weight>
<height>174</height>
</human>
<human>
<weight>89</weight>
<height>187</height>
</human>
</people>
I need to extract an array of weight from it. It can easily be done with string manipulation but there must be a cleaner way to do that with XML parser?
You could use ElementTree (included in the python standard library) and do the following:
import xml.etree.ElementTree
tree = xml.etree.ElementTree.parse("foo.xml")
myArray = [int(x.text) for x in tree.getroot().findall("human/weight")]