Python lxml xpath XPathEvalError: Invalid expression -- why? - python

I'm trying to parse an SVG document with lxml. Here's my code:
nsmap = {
'svg': 'http://www.w3.org/2000/svg',
'xlink': 'http://www.w3.org/1999/xlink',
}
root = etree.XML(svg)
# this works (finds the element with the given ID)
root.xpath('./svg:g/svg:g/svg:g[#id="route_1_edge"]', namespaces=nsmap)
# this yields "XPathEvalError: Invalid expression"
root.xpath('./svg:g/svg:g/svg:g[fn:startswith(#id,"route_1")]', namespaces=nsmap)
Anyone know why the first one works and the second doesn't? If I change the third svg:g to svg:text I don't get an exception, so it seems to be something to do with the g element in particular that it doesn't like, though, again, the simple g[#id="foo"] search works fine.

The "startswith" function is spelled starts-with. Also, omit the fn:.
root.xpath('./svg:g/svg:g/svg:g[starts-with(#id,"route_1")]', namespaces=nsmap)
import lxml.etree as etree
import lxml.builder as builder
nsmap = {
'svg': 'http://www.w3.org/2000/svg',
'xlink': 'http://www.w3.org/1999/xlink',
}
E = builder.ElementMaker(
namespace='http://www.w3.org/2000/svg',
nsmap=nsmap)
root = (
E.root(
E.g(
E.g(
E.g(id = "route_1_edge" )))))
print(etree.tostring(root, pretty_print=True))
print(root.xpath('./svg:g/svg:g/svg:g[#id="route_1_edge"]', namespaces=nsmap))
print(root.xpath('./svg:g/svg:g/svg:g[starts-with(#id,"route_1")]', namespaces=nsmap))
yields
<svg:root xmlns:svg="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
<svg:g>
<svg:g>
<svg:g id="route_1_edge"/>
</svg:g>
</svg:g>
</svg:root>
[<Element {http://www.w3.org/2000/svg}g at 0xb7462c34>]
[<Element {http://www.w3.org/2000/svg}g at 0xb7462be4>]

Related

How to access UBL 2.1 xml tag using python

I need to access the tags in UBL 2.1 and modify them depend on the on the user input on python.
So, I used the ElementTree library to access the tags and modify them.
Here is a sample of the xml code:
<ns0:Invoice xmlns:ns0="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2" xmlns:ns1="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2" xmlns:ns2="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2">
<ns1:ProfileID>reporting:1.0</ns1:ProfileID>
<ns1:ID>0</ns1:ID>
<ns1:UUID>dbdf65eb-5d66-47e6-bb0c-a84bbf7baa30</ns1:UUID>
<ns1:IssueDate>2022-11-05</ns1:IssueDate>
The issue :
I want to access the tags but it is doesn't modifed and enter the loop
I tried both ways:
mytree = ET.parse('test.xml')
myroot = mytree.getroot()
for x in myroot.find({xmlns:ns1=urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2}IssueDate}"):
x.text = '1999'
mytree.write('test.xml')
mytree = ET.parse('test.xml')
myroot = mytree.getroot()
for x in myroot.iter('./Invoice/AllowanceCharge/ChargeIndicator'):
x.text = str('true')
mytree.write('test.xml')
None of them worked and modify the tag.
So the questions is : How can I reach the specific tag and modify it?
If you correct the namespace and the brakets in your for loop it works for a valid XML like (root tag must be closed!):
Input:
<?xml version="1.0" encoding="utf-8"?>
<ns0:Invoice xmlns:ns0="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2" xmlns:ns1="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2" xmlns:ns2="urn:oasis:names:specification:ubl:schema:xsd:CommonAggregateComponents-2">
<ns1:ProfileID>reporting:1.0</ns1:ProfileID>
<ns1:ID>0</ns1:ID>
<ns1:UUID>dbdf65eb-5d66-47e6-bb0c-a84bbf7baa30</ns1:UUID>
<ns1:IssueDate>2022-11-05</ns1:IssueDate>
</ns0:Invoice>
Your repaired code:
import xml.etree.ElementTree as ET
tree = ET.parse('test.xml')
root = tree.getroot()
for elem in root.findall("{urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2}IssueDate"):
elem.text = '1999'
tree.write('test_changed.xml', encoding='utf-8', xml_declaration=True)
ET.dump(root)
Output:
<ns0:Invoice xmlns:ns0="urn:oasis:names:specification:ubl:schema:xsd:Invoice-2" xmlns:ns1="urn:oasis:names:specification:ubl:schema:xsd:CommonBasicComponents-2">
<ns1:ProfileID>reporting:1.0</ns1:ProfileID>
<ns1:ID>0</ns1:ID>
<ns1:UUID>dbdf65eb-5d66-47e6-bb0c-a84bbf7baa30</ns1:UUID>
<ns1:IssueDate>1999</ns1:IssueDate>
</ns0:Invoice>

How to get the xml element as a string with namespace using ElementTree in python?

I need to get the elements from xml as a string. I am trying with below xml format.
<xml>
<prot:data xmlns:prot="prot">
<product-id-template>
<prot:ProductId>PRODUCT_ID</prot:ProductId>
</product-id-template>
<product-name-template>
<prot:ProductName>PRODUCT_NAME</prot:ProductName>
</product-name-template>
<dealer-template>
<xsi:Dealer xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">DEALER</xsi:Dealer>
</dealer-template>
</prot:data>
</xml>
And I tried with below code:
from xml.etree import ElementTree as ET
def get_template(xpath, namespaces):
tree = ET.parse('cdata.xml')
elements = tree.getroot()
for element in elements.findall(xpath, namespaces=namespaces):
return element
namespace = {"prot" : "prot"}
aa = get_template(".//prot:ProductId", namespace)
print(ET.tostring(aa).decode())
Actual output:
<ns0:ProductId xmlns:ns0="prot">PRODUCT_ID</ns0:ProductId>
Expected output:
<prot:ProductId>PRODUCT_ID</prot:ProductId>
I should not remove the xmlns from the document where it presents in the document. And It has to be removed where it not presents. Example product-id-template is not containing the xmlns so it needs to be retrieved without xmlns. And dealer-template contains the xmlns so it needs to be retrieved with xmlns.
How to achieve this?
You can remove xmlns with regex.
import re
# ...
with_ns = ET.tostring(aa).decode()
no_ns = re.sub(' xmlns(:\w+)?="[^"]+"', '', with_ns)
print(no_ns)
UPDATE: You can do a very wild thing. Although I can't recommend it, because I'm not a Python expert.
I just checked the source code and found that I can do this hack:
def my_serialize_xml(write, elem, qnames, namespaces,
short_empty_elements, **kwargs):
ET._serialize_xml(write, elem, qnames,
None, short_empty_elements, **kwargs)
ET._serialize["xml"] = my_serialize_xml
I just defined my_serialize_xml, which calls ElementTree._serialize_xml with namespaces=None. And then, in dictionary ElementTree._serialize, I changed value for key "xml" to my_serialize_xml. So when you call ElementTree.tostring, it will use my_serialize_xml.
If you want to try it, just place the code(above) after from xml.etree import ElementTree as ET (but before using the ET).

Accesing values in xml file with namespaces in python 2.7 lxml

I'm following this link to try to get values of several tags:
Parsing XML with namespace in Python via 'ElementTree'
In this link there is no problem to access to the root tag like this:
import sys
from lxml import etree as ET
doc = ET.parse('file.xml')
namespaces_rdf = {'rdf': 'http://www.w3.org/1999/02/22-rdf-syntax-ns#'} # add more as needed
namespaces_dcat = {'dcat': 'http://www.w3.org/ns/dcat#'} # add more as needed
namespaces_dct = {'dct': 'http://purl.org/dc/terms/'}
print doc.findall('rdf:RDF', namespaces_rdf)
print doc.findall('dcat:Dataset', namespaces_dcat)
print doc.findall('dct:identifier', namespaces_dct)
OUTPUT:
[]
[<Element {http://www.w3.org/ns/dcat#}Dataset at 0x2269b98>]
[]
I get only access to dcat:Dataset, and I can't see how to access the value of rdf:about
And later access to dct:identifier
Of course, once I have accessed to this info, I need to acces to dcat:distribution info
This is my example file, generated with ckanext-dcat:
<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF
xmlns:dct="http://purl.org/dc/terms/"
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:dcat="http://www.w3.org/ns/dcat#"
>
<dcat:Dataset rdf:about="http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01">
<dct:identifier>ec631628-2f46-4f17-a685-d62a37466c01</dct:identifier>
<dct:description>FOO-Description</dct:description>
<dct:title>FOO-title</dct:title>
<dcat:keyword>keyword1</dcat:keyword>
<dcat:keyword>keyword2</dcat:keyword>
<dct:issued rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2014-10-08T08:55:04.566618</dct:issued>
<dct:modified rdf:datatype="http://www.w3.org/2001/XMLSchema#dateTime">2015-06-25T11:04:10.328902</dct:modified>
<dcat:distribution>
<dcat:Distribution rdf:about="http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01/resource/f5707551-6bf3-468f-9a96-b4184cc51d1f">
<dct:title>FOO-title-1</dct:title>
<dct:description>FOO-Description-1</dct:description>
<dcat:accessURL>http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01/resource/f5707551-6bf3-468f-9a96-b4184cc51d1f/download/myxls.xls</dcat:accessURL>
<dct:format>XLS</dct:format>
</dcat:Distribution>
</dcat:distribution>
<dcat:distribution>
<dcat:Distribution rdf:about="http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01/resource/74c1acc8-b2b5-441b-afb2-d072d0d00a7f">
<dct:format>XLS</dct:format>
<dct:title>FOO-title-2</dct:title>
<dct:description>FOO-Description-2</dct:description>
<dcat:accessURL>http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01/resource/74c1acc8-b2b5-441b-afb2-d072d0d00a7f/download/myxls.xls</dcat:accessURL>
</dcat:Distribution>
</dcat:distribution>
</dcat:Dataset>
</rdf:RDF>
Any idea on how to access this info??
Thanks
UPDATE:
Well, I need to access rdf:about in:
<dcat:Dataset rdf:about="http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01">
so with this code taken from:
Parse xml with lxml - extract element value
for node in doc.xpath('//dcat:Dataset', namespaces=namespaces):
# Iterate over attributes
for attrib in node.attrib:
print '#' + attrib + '=' + node.attrib[attrib]
I get this output:
[<Element {http://www.w3.org/ns/dcat#}Dataset at 0x23d8ee0>]
#{http://www.w3.org/1999/02/22-rdf-syntax-ns#}about=http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01
So, the question is:
How can I ask if the attribute is about to take this value, because in other files I have several tags.
UPDATE 2: Fixed how I get about value (clark notations)
for node in doc.xpath('//dcat:Dataset', namespaces=namespaces):
# Iterate over attributes
for attrib in node.attrib:
if attrib.endswith('about'):
#do my jobs
Well, almost finished, but I have last question: I need to know when I access my
<dct:title>
to which belongs, I have:
<dcat:Dataset rdf:about="http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01">
<dct:title>FOO-title</dct:title>
<dcat:Distribution rdf:about="http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01/resource/f5707551-6bf3-468f-9a96-b4184cc51d1f">
<dct:title>FOO-title-1</dct:title>
<dcat:Distribution rdf:about="http://www.myweb.com/dataset/ec631628-2f46-4f17-a685-d62a37466c01/resource/74c1acc8-b2b5-441b-afb2-d072d0d00a7f">
<dct:title>FOO-title-2</dct:title>
If I do something like this I get:
for node in doc.xpath('//dct:title', namespaces=namespaces):
print node.tag, node.text
{http://purl.org/dc/terms/}title FOO-title
{http://purl.org/dc/terms/}title FOO-title-1
{http://purl.org/dc/terms/}title FOO-title-2
Thanks
Use the xpath() method with namespaces named argument:
namespaces = {
'rdf': 'http://www.w3.org/1999/02/22-rdf-syntax-ns#',
'dcat': 'http://www.w3.org/ns/dcat#',
'dct': 'http://purl.org/dc/terms/'
}
print(doc.xpath('//rdf:RDF', namespaces=namespaces))
print(doc.xpath('//dcat:Dataset', namespaces=namespaces))
print(doc.xpath('//dct:identifier', namespaces=namespaces))

python parsing xml with ElementTree doesn't give interested result

I have an xml file like this
<?xml version="1.0"?>
<sample>
<text>My name is <b>Wrufesh</b>. What is yours?</text>
</sample>
I have a python code like this
import xml.etree.ElementTree as ET
tree = ET.parse('sample.xml')
root = tree.getroot()
for child in root:
print child.text()
I only get
'My name is' as an output.
I want to get
'My name is <b>Wrufesh</b>. What is yours?' as an output.
What can I do?
You can get your desired output using using ElementTree.tostringlist():
>>> import xml.etree.ElementTree as ET
>>> root = ET.parse('sample.xml').getroot()
>>> l = ET.tostringlist(root.find('text'))
>>> l
['<text', '>', 'My name is ', '<b', '>', 'Wrufesh', '</b>', '. What is yours?', '</text>', '\n']
>>> ''.join(l[2:-2])
'My name is <b>Wrufesh</b>. What is yours?'
I wonder though how practical this is going to be for generic use.
I don't think treating tag in xml as a string is right. You can access the text part of xml like this:
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import xml.etree.ElementTree as ET
tree = ET.parse('sample.xml')
root = tree.getroot()
text = root[0]
for i in text.itertext():
print i
# As you can see, `<b>` and `</b>` is a pair of tags but not strings.
print text._children
I would suggest pre-processing the xml file to wrap elements under <text> element in CDATA. You should be able to read the values without a problem afterwards.
<text><![CDATA[<My name is <b>Wrufesh</b>. What is yours?]]></text>

xml file parsing in python

xml file :
<global>
<rtmp>
<fcsapp>
<password>
<key>hello123</key>
<key>check123</key>
</password>
</fcsapp>
</rtmp>
</global>
python code : To obtain all the key tag values.
hello123
check123
using xml.etree.ElementTree
for streams in xmlRoot.iter('global'):
xpath = "/rtmp/fcsapp/password"
tag = "key"
for child in streams.findall(xpath):
resultlist.append(child.find(tag).text)
print resultlist
The output obtained is [hello123], but I want it to display both ([hello123, check123])
How do I obtain this?
Using lxml and cssselect I would do it like this:
>>> from lxml.html import fromstring
>>> doc = fromstring(open("foo.xml", "r").read())
>>> doc.cssselect("password key")
[<Element key at 0x7f77a6786cb0>, <Element key at 0x7f77a6786d70>]
>>> [e.text for e in doc.cssselect("password key")]
['hello123 \n ', 'check123 \n ']
With lxml and xpath You can do it in the following way:
from lxml import etree
xml = """
<global>
<rtmp>
<fcsapp>
<password>
<key>hello123</key>
<key>check123</key>
</password>
</fcsapp>
</rtmp>
</global>
"""
tree = etree.fromstring(xml)
result = tree.xpath('//password/key/text()')
print result # ['hello123', 'check123']
try beautifulsoup package "https://pypi.python.org/pypi/BeautifulSoup"
using xml.etree.ElementTree
for streams in xmlRoot.iter('global'):
xpath = "/rtmp/fcsapp/password"
tag = "key"
for child in streams.iter(tag):
resultlist.append(child.text)
print resultlist
have to iter over the "key" tag in for loop to obtain the desired result. The above code solves the problem.

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