If you want to preserve comments in an XML file with ElementTree, you can use the PIParser from http://effbot.org/zone/element-pi.htm
So if I have a file containing
<?xml version="1.0" encoding="iso-8859-1"?>
<!-- This is a comment -->
<root>
<foo>Hello World</foo>
</root>
<!-- That's all, folks -->
then the two comments will be preserved.
PIParser wraps the xml in another <document> node, so there is something to contain any comments that come outside the root node. The two comments are just two more elements contained in <document>.
But then how should I output the xml? I use code like this to output the contents of <document> without outputting the <document> tag itself:
file.write('<?xml version="1.0" encoding="%s"?>\n' % encoding)
doc = tree.getroot()
for child in doc:
file.write(ET.tostring(child, encoding, method))
file.write("\n")
Now, that seems to work if encoding is "utf-8". The tostring() method does not output one of those <?xml...?> lines, presumably because utf-8 is the default. That's why I wrote the <?xml...?> explicitly with file.write() above. But if encoding is "iso-8859-1" then tostring() puts a <?xml version="1.0" encoding="iso-8859-1"?> at the start of every element for which it is called! So I get one in front of every comment outside the root node, and another in front of the root node itself. I don't want that, I only want one at the top of the file. But instead of getting the xml as shown above, I get
<?xml version="1.0" encoding="iso-8859-1"?>
<?xml version='1.0' encoding='iso-8859-1'?>
<!-- This is a comment -->
<?xml version='1.0' encoding='iso-8859-1'?>
<root>
<foo>Hello World</foo>
</root>
<?xml version='1.0' encoding='iso-8859-1'?>
<!-- That's all, folks -->
How do I control whether tostring() outputs a <?xml...?>? Or, should I be doing this another way?
Related
I would like to pass a certain parameter to an xml, so instead of being a raw xml with all the values by the creation of it, I'd like to change one with a parameter (a user input, for example).
Ideally, I was looking for something like <title> ¶m1 </title>and be able later on to pass whatever param I would like, but I guess it cannot be done.
So like passing a parameter cannot be done (or at least from what I have searched), I thought about editing the xml after it's created.
I have searched mostly with beautifulsoup, because it is what I want to use (and what I am using). This is only a little bit of my project.
for example this and this are some of my research).
So this is the function I am trying to do:
We have an xml, we find the part we want to edit, and we edit it (I know that to access it, it needs to be an integer pruebaEdit[anyString]is not correct.
def editXMLTest():
editTest="""<?xml version="1.0" ?>
<books>
<book>
<title>moon</title>
<author>louis</author>
<price>8.50</price>
</book>
</books>
"""
soup =BeautifulSoup(editTest)
for tag in soup.find_all('title'):
print (tag.string, '\n')
#tag.string='invented title'
editTest[tag]='invented title' #I know it has to be an integer, not a string
print()
print(editTest)
My expected output should be in the xml: <title>invented title</title> instead of <title>moon</title>.
Edit: added this to my research
you have to print the results or soup not original string editTest
for tag in soup.find_all('title'):
print (tag.string, '\n')
tag.string='invented title'
print(soup)
Using entity references like ¶m; is the closest thing available in XML itself, but it's not very flexible because the entity expansions are defined in a DTD file rather than being supplied programmatically to the XML parser. Some parsers (I don't know the Python situation) allow you to supply an EntityResolver which can resolve entity references programmatically, but it wouldn't be my first choice of approach.
There are of course templating languages that allow XML to be constructed programmatically. XSLT is the most obvious choice; it probably does a lot more than you need, but that's not necessarily a drawback. Some other options are listed at https://en.wikipedia.org/wiki/Comparison_of_web_template_engines -- including a handful for the Python environment. Unfortunately many of these tools, in my experience, are not particularly well documented or supported, so do your research carefully.
With Python's lxml that can run XSLT 1.0 scripts and also the parsing engine to BeautifulSoup, you can pass parameters to modify XML files as needed. Simply set the <xsl:param> in XSLT script and in Python pass value via strparam:
XSLT (save as .xsl file, a special .xml file)
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output indent="yes" omit_xml_declaration="no"/>
<xsl:strip-space elements="*"/>
<!-- INITIALIZE PARAMETER -->
<xsl:param name="new_title" />
<!-- IDENTITY TRANSFORM -->
<xsl:template match="#*|node()">
<xsl:copy>
<xsl:apply-templates select="#*|node()"/>
</xsl:copy>
</xsl:template>
<!-- REWRITE TITLE TEXT -->
<xsl:template match="title">
<xsl:copy>
<xsl:value-of select="$new_title"/>
</xsl:copy>
</xsl:template>
</xsl:stylesheet>
Python (see output below as comment)
import lxml.etree as et
txt = '''<books>
<book>
<title>moon</title>
<author>louis</author>
<price>8.50</price>
</book>
</books>'''
# LOAD XSL SCRIPT
xml = et.fromstring(txt)
xsl = et.parse('/path/to/XSLTScript.xsl')
transform = et.XSLT(xsl)
# PASS PARAMETER TO XSLT
n = et.XSLT.strparam('invented title')
result = transform(doc, new_title=n)
print(result)
# <?xml version="1.0"?>
# <books>
# <book>
# <title>invented title</title>
# <author>louis</author>
# <price>8.50</price>
# </book>
# </books>
# SAVE XML TO FILE
with open('Output.xml', 'wb') as f:
f.write(result)
Pyfiddle Demo (be sure to click run and check output)
Use <xsl> tag to pass a parameter in xml
Input xml file:
<?xml version="1.0"?>
<res:testcases xmlns:res="urn:testcases" id="a1e4bfdb-40a2-485c-a1ac-54d220056dd5" type="MODEL">
<mode>PRESSURE_CONTROL</mode>
<category>ADULT</category>
<testcase id="1" type="UNIQUE">
<parameter id="PEEP" value="1.0">true</parameter>
<parameter id="CMV_FREQ" value="4.0">true</parameter>
<parameter id="PRESS_ABOVE_PEEP" value="0.0">true</parameter>
<parameter id="I_E_RATIO" value="0.1">false</parameter>
</testcase>
</res:testcases>
Python Code:
import xml.etree.ElementTree as ET
tree = ET.parse('/home/AlAhAb65/Desktop/input.xml')
root = tree.getroot()
root.attrib['type'] = 'AVA'
tree.write('/home/AlAhAb65/Desktop/output1.xml')
Output xml file:
<ns0:testcases id="a1e4bfdb-40a2-485c-a1ac-54d220056dd5" type="AVA" xmlns:ns0="urn:testcases">
<mode>PRESSURE_CONTROL</mode>
<category>ADULT</category>
<testcase id="1" type="UNIQUE">
<parameter id="PEEP" value="1.0">true</parameter>
<parameter id="CMV_FREQ" value="4.0">true</parameter>
<parameter id="PRESS_ABOVE_PEEP" value="0.0">true</parameter>
<parameter id="I_E_RATIO" value="0.1">false</parameter>
</testcase>
</ns0:testcases>
The problem is when I am copying and writing the output xml file 3 unexpected things happen. They are given below:
1. The first line from the input xml file is removed automatically
2. In second line (in input), the text 'res' is replaced with 'ns0'. Same happens while closing the tag
3. The order of the attribute (of the second line of input) is changed.
But I want to write (as output) the exact copy of xml file that I got as an input. Please help me in this regard.
W3 has defined a Canonical XML standard. Documents written in this format can be faithfully round-tripped by any C14N-compliant toolchain.
In the case of lxml.etree (a more capable implementation of the ElementTree API with C14N support), this means that you need to do two things:
Convert your original input document into C14N form.
Use the ElementTree.write_c14n() call to generate your output document.
A C14N-form version of your input file will look like so (generated by the xmlstarlet c14n command):
<res:testcases xmlns:res="urn:testcases" id="a1e4bfdb-40a2-485c-a1ac-54d220056dd5" type="MODEL">
<mode>PRESSURE_CONTROL</mode>
<category>ADULT</category>
<testcase id="1" type="UNIQUE">
<parameter id="PEEP" value="1.0">true</parameter>
<parameter id="CMV_FREQ" value="4.0">true</parameter>
<parameter id="PRESS_ABOVE_PEEP" value="0.0">true</parameter>
<parameter id="I_E_RATIO" value="0.1">false</parameter>
</testcase>
</res:testcases>
...and an appropriately modified version of your code:
#!/usr/bin/env python
import lxml.etree
tree = lxml.etree.parse('input.xml')
root = tree.getroot()
root.attrib['type'] = 'AVA'
tree.write_c14n('output1.xml')
If you add an XML declaration (the <?xml version="1.0"?> line), you will be noncomplaint with the C14N standard. As such, this is something you absolutely should not do. If you really, really want to do this wrongheaded thing...
Don't.
But if you must, you'd do it like so:
outfile = open('output1.xml', 'w')
outfile.write('<?xml version="1.0"?>\n')
tree.write_c14n(outfile)
outfile.close()
From the documentation page, the XML declaration can be added like this:
tree.write('/home/AlAhAb65/Desktop/output1.xml', xml_declaration=True)
You should also add the encoding because the default one is us-ascii:
tree.write('/home/AlAhAb65/Desktop/output1.xml', encoding='utf-8', xml_declaration=True)
Or you can retrieve the encoding from the original file, but in any case you will get a different XML declaration, probably something like this:
<?xml version="1.0" encoding="UTF-8"?>
Or you can manually add the XML declaration. Anyway a slight declaration mismatch should not be a problem for any robust XML parser as long as the declared encoding is coherent with the real encoding.
Attribute order is not significant in XML, so the information is probably lost when the file is parsed within the API. There is probably no simple way to make this work when processing the file through the standard ElementTree API. You would probably better have to go with lxml C14N support if you want to do minor changes to the file.
The namespace prefixes are changed by default in ElementTree. To prevent this behavior, you can switch to lxml which seems to preserve namespace prefixes by default:
Because etree is built on top of libxml2, which is namespace prefix aware, etree preserves namespaces declarations and prefixes while ElementTree tends to come up with its own prefixes (ns0, ns1, etc). When no namespace prefix is given, however, etree creates ElementTree style prefixes as well.
Switching to lxml is a good idea in any case, but the changes you observe should not be a problem if the program reading the file at the other end is XML compliant enough. Unfortunately a lot of XPath processors have issues with namespace prefixes changes...
I am using lxml with
tree.write(xmlFileOut, pretty_print = True, xml_declaration = True, encoding='UTF-8'
to write out my opened and edited xml file, but I absolutely need to have the xml declaration as
<?xml version=“1.0” encoding=“UTF-8”?>
and NOT
<?xml version='1.0' encoding='UTF-8'?>
Now I know they are exactly the same when it comes to xml, but I am dealing with a very tricky customer who absolutely has to have " in the declaration and not '. I have searched everywhere but can't find the answer.
Could I create it and add it in myself to the head of the xml somehow?
Could I tell lxml that this is what I need as an xml declaration?
This is a site for coding questions, not a site for advice in dealing with tricky customers. Your customer is wrong; your problem is political/commercial, not technical.
Here is the original xml file:
<?xml version="1.0" encoding="UTF-8"?>
<TVAMain xml:lang="en-GB" xmlns="urn:tva:metadata:2010" xmlns:tva2="urn:tva:metadata:extended:2010" xmlns:yv="http://refdata.youview.com/schemas/Metadata/2012-10-16" xmlns:mpeg7="urn:tva:mpeg7:2008" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://refdata.youview.com/schemas/Metadata/2012-09-26 ../schemas/youview_metadata_2012-09-26.xsd">
<!-- -->
<ProgramDescription> .............................
I changes some of the content of the xml(but not the one I post here, those codes should be unchanged), then write to a new xml file, but the new xml file content become like this:
<?xml version='1.0' encoding='UTF-8'?>
<TVAMain xmlns="urn:tva:metadata:2010" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://refdata.youview.com/schemas/Metadata/2012-09-26 ../schemas/youview_metadata_2012-09-26.xsd" xml:lang="en-GB">
<ProgramDescription>....................
you can see that the some contents are lost, and the order is also changed, what should I do in order to avoid any changes to xml?
Attributes on XML tags do not have a fixed order, changing their ordering doesn't change their meaning.
ElementTree will only write out namespace qualifiers for namespaces actually in use. Your example is very brief, but I suspect it doesn't make use of the yv and mpeg7 namespaces at all.
I have created an XML document with the following contents.
<books>
<book id="1">
<title>Title01</title>
<authors/>
<pages>
<page>Page01</page>
<page>Page02</page>
<page>Page03</page>
<page>Page04</page>
<page>Page05</page>
</pages>
</book>
<book id="2">
<title>Title02</title>
<authors/>
<pages>
<page>Page01</page>
<page>Page02</page>
<page>Page03</page>
<page>Page04</page>
<page>Page05</page>
</pages>
</book>
</books>
I then use a Python script to split up and write the individual books into separate files;however, the resulting files are not XML files because they do not have the XML declaration. Is there a way of creating XML files in Python?
The idea is to ensure that each file has the XML declaration as show below.
<?xml version="1.0" encoding="ISO-8859-1" ?>
<book id="1">
<title>Title01</title>
<authors/>
<pages>
<page>Page01</page>
<page>Page02</page>
<page>Page03</page>
<page>Page04</page>
<page>Page05</page>
</pages>
</book>
Why don't you write the xml declaration to each book file before you write the book entry?
Encode your files in UTF-8 instead of some legacy encoding like ISO-8859-1. Then you don't need an XML declaration.
You should look into the xml.etree.ElementTree module. The link is for Python 3, but it was included way before that. I use it in Python 2.5, so you should be ok.
Also, I have had good results with xml.dom.minidom. Once you have built a Document (by adding elements with createElement('ELEM_NAME'), you just write it to a stream with mydoc.toprettyxml().