Develop Reference

Parsing text from XML node in Python

I'm trying to extract URLs from a sitemap like this: https://www.bestbuy.com/sitemap_c_0.xml.gz
I've unzipped and saved the .xml.gz file as an .xml file. The structure looks like this:
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xhtml="http://www.w3.org/1999/xhtml" xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd">
<url>
<loc>https://www.bestbuy.com/</loc>
<priority>0.0</priority>
</url>
<url>
<loc>https://www.bestbuy.com/site/3d-printers/3d-printer-filament/pcmcat335400050008.c?id=pcmcat335400050008</loc>
<priority>0.0</priority>
</url>
<url>
<loc>https://www.bestbuy.com/site/3d-printers/3d-printing-accessories/pcmcat748300527647.c?id=pcmcat748300527647</loc>
<priority>0.0</priority>
</url>
I'm attempting to use ElementTree to extract all of the URLs within the loc nodes throughout this file, but struggling to get it working right.
Per the documentation, I'm trying something like this:
import xml.etree.ElementTree as ET
tree = ET.parse('my_local_filepath')
root = tree.getroot()
value = root.findall(".//loc")
However, nothing gets loaded into value. My goal is to extract all of the URLs between the loc nodes and print it out into a new flat file. Where am I going wrong?

You were close in your attempt but like mzjn said in a comment, you didn't account for the default namespace (xmlns="http://www.sitemaps.org/schemas/sitemap/0.9").
Here's an example of how to account for the namespace:
import xml.etree.ElementTree as ET
tree = ET.parse('my_local_filepath')
ns = {"sm": "http://www.sitemaps.org/schemas/sitemap/0.9"}
for elem in tree.findall(".//sm:loc", ns):
print(elem.text)
output:
https://www.bestbuy.com/
https://www.bestbuy.com/site/3d-printers/3d-printer-filament/pcmcat335400050008.c?id=pcmcat335400050008
https://www.bestbuy.com/site/3d-printers/3d-printing-accessories/pcmcat748300527647.c?id=pcmcat748300527647
Note that I used the namespace prefix sm, but you could use any NCName.
See here for more information on parsing XML with namespaces in ElementTree.

We can iterate through the URLs, toss them into a list and write them to a file as such:
from xml.etree import ElementTree as ET
tree = ET.parse('test.xml')
root = tree.getroot()
name_space = '{http://www.sitemaps.org/schemas/sitemap/0.9}'
urls = []
for child in root.iter():
for block in child.findall('{}url'.format(name_space)):
for url in block.findall('{}loc'.format(name_space)):
urls.append('{}\n'.format(url.text))
with open('sample_urls.txt', 'w+') as f:
f.writelines(urls)
note we need to append the name space from the open urlset definition to properly parse the xml

Parse an elementTree to return a string in XML form - Python

is there a way to parse an entire ElementTree from a file and return it as a string in python? I would like to read the entire file into a single string value, for example grabbing the entire output of dump(tree)? Any help or advice would be greatly appreciated!
xml
import xml.etree.ElementTree as ET
print "Enter a filename"
filename = input()
tree = ET.parse(filename)
string = tree.tostring() ##is there a way to do something like this?
test.xml
<data>
<serial>
<serial name = "serial">SN001</serial>
</serial>
<items>
<item>Test1 = Failed</item>
<item>Test2 = Passed</item>
<item>Test3 = Passed</item>
</items>
</data>

tostring is a module function, not a method.
string = ET.tostring(tree.getroot())

How to write XML declaration using xml.etree.ElementTree

I am generating an XML document in Python using an ElementTree, but the tostring function doesn't include an XML declaration when converting to plaintext.
from xml.etree.ElementTree import Element, tostring
document = Element('outer')
node = SubElement(document, 'inner')
node.NewValue = 1
print tostring(document) # Outputs "<outer><inner /></outer>"
I need my string to include the following XML declaration:
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
However, there does not seem to be any documented way of doing this.
Is there a proper method for rendering the XML declaration in an ElementTree?

I am surprised to find that there doesn't seem to be a way with ElementTree.tostring(). You can however use ElementTree.ElementTree.write() to write your XML document to a fake file:
from io import BytesIO
from xml.etree import ElementTree as ET
document = ET.Element('outer')
node = ET.SubElement(document, 'inner')
et = ET.ElementTree(document)
f = BytesIO()
et.write(f, encoding='utf-8', xml_declaration=True)
print(f.getvalue()) # your XML file, encoded as UTF-8
See this question. Even then, I don't think you can get your 'standalone' attribute without writing prepending it yourself.

I would use lxml (see http://lxml.de/api.html).
Then you can:
from lxml import etree
document = etree.Element('outer')
node = etree.SubElement(document, 'inner')
print(etree.tostring(document, xml_declaration=True))

If you include the encoding='utf8', you will get an XML header:
xml.etree.ElementTree.tostring writes a XML encoding declaration with encoding='utf8'
Sample Python code (works with Python 2 and 3):
import xml.etree.ElementTree as ElementTree
tree = ElementTree.ElementTree(
ElementTree.fromstring('<xml><test>123</test></xml>')
)
root = tree.getroot()
print('without:')
print(ElementTree.tostring(root, method='xml'))
print('')
print('with:')
print(ElementTree.tostring(root, encoding='utf8', method='xml'))
Python 2 output:
$ python2 example.py
without:
<xml><test>123</test></xml>
with:
<?xml version='1.0' encoding='utf8'?>
<xml><test>123</test></xml>
With Python 3 you will note the b prefix indicating byte literals are returned (just like with Python 2):
$ python3 example.py
without:
b'<xml><test>123</test></xml>'
with:
b"<?xml version='1.0' encoding='utf8'?>\n<xml><test>123</test></xml>"

xml_declaration Argument
Is there a proper method for rendering the XML declaration in an ElementTree?
YES, and there is no need of using .tostring function. According to ElementTree Documentation, you should create an ElementTree object, create Element and SubElements, set the tree's root, and finally use xml_declaration argument in .write function, so the declaration line is included in output file.
You can do it this way:
import xml.etree.ElementTree as ET
tree = ET.ElementTree("tree")
document = ET.Element("outer")
node1 = ET.SubElement(document, "inner")
node1.text = "text"
tree._setroot(document)
tree.write("./output.xml", encoding = "UTF-8", xml_declaration = True)
And the output file is:
<?xml version='1.0' encoding='UTF-8'?>
<outer><inner>text</inner></outer>

I encounter this issue recently, after some digging of the code, I found the following code snippet is definition of function ElementTree.write
def write(self, file, encoding="us-ascii"):
assert self._root is not None
if not hasattr(file, "write"):
file = open(file, "wb")
if not encoding:
encoding = "us-ascii"
elif encoding != "utf-8" and encoding != "us-ascii":
file.write("<?xml version='1.0' encoding='%s'?>\n" %
encoding)
self._write(file, self._root, encoding, {})
So the answer is, if you need write the XML header to your file, set the encoding argument other than utf-8 or us-ascii, e.g. UTF-8

Easy
Sample for both Python 2 and 3 (encoding parameter must be utf8):
import xml.etree.ElementTree as ElementTree
tree = ElementTree.ElementTree(ElementTree.fromstring('<xml><test>123</test></xml>'))
root = tree.getroot()
print(ElementTree.tostring(root, encoding='utf8', method='xml'))
From Python 3.8 there is xml_declaration parameter for that stuff:
New in version 3.8: The xml_declaration and default_namespace
parameters.
xml.etree.ElementTree.tostring(element, encoding="us-ascii",
method="xml", *, xml_declaration=None, default_namespace=None,
short_empty_elements=True) Generates a string representation of an XML
element, including all subelements. element is an Element instance.
encoding 1 is the output encoding (default is US-ASCII). Use
encoding="unicode" to generate a Unicode string (otherwise, a
bytestring is generated). method is either "xml", "html" or "text"
(default is "xml"). xml_declaration, default_namespace and
short_empty_elements has the same meaning as in ElementTree.write().
Returns an (optionally) encoded string containing the XML data.
Sample for Python 3.8 and higher:
import xml.etree.ElementTree as ElementTree
tree = ElementTree.ElementTree(ElementTree.fromstring('<xml><test>123</test></xml>'))
root = tree.getroot()
print(ElementTree.tostring(root, encoding='unicode', method='xml', xml_declaration=True))

The minimal working example with ElementTree package usage:
import xml.etree.ElementTree as ET
document = ET.Element('outer')
node = ET.SubElement(document, 'inner')
node.text = '1'
res = ET.tostring(document, encoding='utf8', method='xml').decode()
print(res)
the output is:
<?xml version='1.0' encoding='utf8'?>
<outer><inner>1</inner></outer>

Another pretty simple option is to concatenate the desired header to the string of xml like this:
xml = (bytes('<?xml version="1.0" encoding="UTF-8"?>\n', encoding='utf-8') + ET.tostring(root))
xml = xml.decode('utf-8')
with open('invoice.xml', 'w+') as f:
f.write(xml)

I would use ET:
try:
from lxml import etree
print("running with lxml.etree")
except ImportError:
try:
# Python 2.5
import xml.etree.cElementTree as etree
print("running with cElementTree on Python 2.5+")
except ImportError:
try:
# Python 2.5
import xml.etree.ElementTree as etree
print("running with ElementTree on Python 2.5+")
except ImportError:
try:
# normal cElementTree install
import cElementTree as etree
print("running with cElementTree")
except ImportError:
try:
# normal ElementTree install
import elementtree.ElementTree as etree
print("running with ElementTree")
except ImportError:
print("Failed to import ElementTree from any known place")
document = etree.Element('outer')
node = etree.SubElement(document, 'inner')
print(etree.tostring(document, encoding='UTF-8', xml_declaration=True))

This works if you just want to print. Getting an error when I try to send it to a file...
import xml.dom.minidom as minidom
import xml.etree.ElementTree as ET
from xml.etree.ElementTree import Element, SubElement, Comment, tostring
def prettify(elem):
rough_string = ET.tostring(elem, 'utf-8')
reparsed = minidom.parseString(rough_string)
return reparsed.toprettyxml(indent=" ")

Including 'standalone' in the declaration
I didn't found any alternative for adding the standalone argument in the documentation so I adapted the ET.tosting function to take it as an argument.
from xml.etree import ElementTree as ET
# Sample
document = ET.Element('outer')
node = ET.SubElement(document, 'inner')
et = ET.ElementTree(document)
# Function that you need
def tostring(element, declaration, encoding=None, method=None,):
class dummy:
pass
data = []
data.append(declaration+"\n")
file = dummy()
file.write = data.append
ET.ElementTree(element).write(file, encoding, method=method)
return "".join(data)
# Working example
xdec = """<?xml version="1.0" encoding="UTF-8" standalone="no" ?>"""
xml = tostring(document, encoding='utf-8', declaration=xdec)

How to add an element to xml file by using elementtree

I've a xml file, and I'm trying to add additional element to it.
the xml has the next structure :
<root>
<OldNode/>
</root>
What I'm looking for is :
<root>
<OldNode/>
<NewNode/>
</root>
but actually I'm getting next xml :
<root>
<OldNode/>
</root>
<root>
<OldNode/>
<NewNode/>
</root>
My code looks like that :
file = open("/tmp/" + executionID +".xml", 'a')
xmlRoot = xml.parse("/tmp/" + executionID +".xml").getroot()
child = xml.Element("NewNode")
xmlRoot.append(child)
xml.ElementTree(root).write(file)
file.close()
Thanks.

You opened the file for appending, which adds data to the end. Open the file for writing instead, using the w mode. Better still, just use the .write() method on the ElementTree object:
tree = xml.parse("/tmp/" + executionID +".xml")
xmlRoot = tree.getroot()
child = xml.Element("NewNode")
xmlRoot.append(child)
tree.write("/tmp/" + executionID +".xml")
Using the .write() method has the added advantage that you can set the encoding, force the XML prolog to be written if you need it, etc.
If you must use an open file to prettify the XML, use the 'w' mode, 'a' opens a file for appending, leading to the behaviour you observed:
with open("/tmp/" + executionID +".xml", 'w') as output:
output.write(prettify(tree))
where prettify is something along the lines of:
from xml.etree import ElementTree
from xml.dom import minidom
def prettify(elem):
"""Return a pretty-printed XML string for the Element.
"""
rough_string = ElementTree.tostring(elem, 'utf-8')
reparsed = minidom.parseString(rough_string)
return reparsed.toprettyxml(indent=" ")
e.g. the minidom prettifying trick.

Python ElementTree parsing unbound prefix error

I am learning ElementTree in python. Everything seems fine except when I try to parse the xml file with prefix:
test.xml:
<?xml version="1.0"?>
<abc:data>
<abc:country name="Liechtenstein" rank="1" year="2008">
</abc:country>
<abc:country name="Singapore" rank="4" year="2011">
</abc:country>
<abc:country name="Panama" rank="5" year="2011">
</abc:country>
</abc:data>
When I try to parse the xml:
import xml.etree.ElementTree as ET
tree = ET.parse('test.xml')
I got the following error:
xml.etree.ElementTree.ParseError: unbound prefix: line 2, column 0
Do I need to specify something in order to parse a xml file with prefix?

Add the abc namespace to your xml file.
<?xml version="1.0"?>
<abc:data xmlns:abc="your namespace">

I encountered the same issue while processing xml file. You can use below code before parse your XML file. This will resolve your issue.
parser1 = etree.XMLParser(encoding="utf-8", recover=True)
tree1 = ElementTree.parse('filename.xml', parser1)

See if this works:
from bs4 import BeautifulSoup
xml_file = "test.xml"
with open(xml_file, "r", encoding="utf8") as f:
contents = f.read()
soup = BeautifulSoup(contents, "xml")
items = soup.find_all("country")
print (items)
The above will produce an array which you can then manipulate to achieve your aim (e.g. remove html tags etc.):
[<country name="Liechtenstein" rank="1" year="2008">
</country>, <country name="Singapore" rank="4" year="2011">
</country>, <country name="Panama" rank="5" year="2011">
</country>]