How to update/modify an XML file in python?

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I have an XML document that I would like to update after it already contains data.

I thought about opening the XML file in "a" (append) mode. The problem is that the new data will be written after the root closing tag.

How can I delete the last line of a file, then start writing data from that point, and then close the root tag?

Of course I could read the whole file and do some string manipulations, but I don't think that's the best idea..

Thanks for your time.

The quick and easy way, which you definitely should not do (see below), is to read the whole file into a list of strings using readlines(). I write this in case the quick and easy solution is what you're looking for.

Just open the file using open(), then call the readlines() method. What you'll get is a list of all the strings in the file. Now, you can easily add strings before the last element (just add to the list one element before the last). Finally, you can write these back to the file using writelines().

An example might help:

my_file = open(filename, "r")
lines_of_file = my_file.readlines()
lines_of_file.insert(-1, "This line is added one before the last line")
my_file.writelines(lines_of_file)

The reason you shouldn't be doing this is because, unless you are doing something very quick n' dirty, you should be using an XML parser. This is a library that allows you to work with XML intelligently, using concepts like DOM, trees, and nodes. This is not only the proper way to work with XML, it is also the standard way, making your code both more portable, and easier for other programmers to understand.

Tim's answer mentioned checking out xml.dom.minidom for this purpose, which I think would be a great idea.

How to edit an XML file in Python?, Which XML parser to choose is up to you, but here is how you can approach this problem with xml.etree.ElementTree : the idea is to iterate over  Now we will create a python script that will read the attached XML file and modify any node value in the XML content and update the same XML file. XML is an inherently hierarchical data format, and the most natural way to represent it is with a tree. We will be parsing the XML data using xml.etree.ElementTree.

Using ElementTree:

import xml.etree.ElementTree

# Open original file
et = xml.etree.ElementTree.parse('file.xml')

# Append new tag: <a x='1' y='abc'>body text</a>
new_tag = xml.etree.ElementTree.SubElement(et.getroot(), 'a')
new_tag.text = 'body text'
new_tag.attrib['x'] = '1' # must be str; cannot be an int
new_tag.attrib['y'] = 'abc'

# Write back to file
#et.write('file.xml')
et.write('file_new.xml')

note: output written to file_new.xml for you to experiment, writing back to file.xml will replace the old content.

IMPORTANT: the ElementTree library stores attributes in a dict, as such, the order in which these attributes are listed in the xml text will NOT be preserved. Instead, they will be output in alphabetical order. (also, comments are removed. I'm finding this rather annoying)

ie: the xml input text <b y='xxx' x='2'>some body</b> will be output as <b x='2' y='xxx'>some body</b>(after alphabetising the order parameters are defined)

This means when committing the original, and changed files to a revision control system (such as SVN, CSV, ClearCase, etc), a diff between the 2 files may not look pretty.

19.7. xml.etree.ElementTree — The ElementTree XML API, Changed in version 2.7: The ElementTree API is updated to 1.3. We'll be using the following XML document as the sample data for this section: fields (such as Element.text ), adding and modifying attributes ( Element.set() method), as well  It worked in python 2.7 modifying an .xml file named "b.xml" located in folder "a", where "a" was located in the "working folder" of python. It outputs the new modified file as "c.xml" in folder "a", without yielding encoding errors (for me) in further use outside of python 2.7.

Useful Python XML parsers:

  1. Minidom - functional but limited
  2. ElementTree - decent performance, more functionality
  3. lxml - high-performance in most cases, high functionality including real xpath support

Any of those is better than trying to update the XML file as strings of text.

What that means to you:

Open your file with an XML parser of your choice, find the node you're interested in, replace the value, serialize the file back out.

Modifying an XML file with Python using xml.etree.ElementTree , This module uses the parse function to create a DOM object from our XML file. change the name of an attribute and modify its value, and how to add an extra  Changing attribute value of an XML file using Python is similar to changing the element value. In this article we will see how to iterate through an xml file and change some of the attribute values based on certain conditions. Example – Change XML Attribute using Python. Let us consider the below xml file for our example.

While I agree with Tim and Oben Sonne that you should use an XML library, there are ways to still manipulate it as a simple string object.

I likely would not try to use a single file pointer for what you are describing, and instead read the file into memory, edit it, then write it out.:

inFile = open('file.xml', 'r')
data = inFile.readlines()
inFile.close()
# some manipulation on `data`
outFile = open('file.xml', 'w')
outFile.writelines(data)
outFile.close()

Reading and Writing XML Files in Python, After executing the above code, you will be able to see a new file has been created with the updated results. set()-Python XML Parsing Tutorial-  I want to update xml file with new information by using lxml library. For example, I have this code: >>> from lxml import etree >>> >>> tree = etree.parse('books.xml')

What you really want to do is use an XML parser and append the new elements with the API provided.

Then simply overwrite the file.

The easiest to use would probably be a DOM parser like the one below:

http://docs.python.org/library/xml.dom.minidom.html

How to Parse and Modify XML in Python?, Modifying XML using Python programming language means updating or modifying an existing XML file or XML string using Python. Extensible  I have n xml file in which I want to change three elements. It's the first, eighth and tenth <string> element. so the easiest approach, I guess, would be like this (But I am open to any other suggestions, Thanks!!):

Modifying XML using Python, You'll learn more about XML and you'll get introduced to the Python Next, you'll learn how you can modify an XML file; And; You'll utilize xpath Then, print out the attributes of your variable to see your change. You can  ElementTree is also great for writing data to XML files. The code below shows how to create an XML file with the same structure as the file we used in the previous examples. The steps are: Create an element, which will act as our root element. In our case the tag for this element is "data".

Python XML with ElementTree, Today we will look into python ElementTree XML API and learn how to use it to parse XML file as well as modify and create XML  I want to be able to edit file that is not in txt, xml etc format. I mean how to edit wit python a file that has xml structure and can be opened in notepad++. I have file with extension .sdlxliff. This file can be opened in notepad++ without any problem. XLF files can be also edited in notepad. How to edit that kind of files using python.

Python XML Parser - ElementTree, Python enables you to parse and modify XML document. In order to parse XML document you need to have the entire XML document in  XML stands for eXtensible Markup Language. It was designed to store and transport small to medium amounts of data and is widely used for sharing structured information. Python enables you to parse and modify XML document. In order to parse XML document you need to have the entire XML document in memory. In this tutorial, we will see how we can

Comments
  • "Of course I could read the only file and the string manipulations" - I'm not sure I understood that last part, could you please rephrase it?
  • editing XML without using one of the parsers is a huge code smell. I have had to work around others releasing software that does this and it is an awful kludge. If it is XML then XML has certain properties that should be adhered to - like being able to play around with whitespace - moving tags but keeping the same semantic meaning of the XML, or adding XML comments. The resultant program becomes brittle, likely to fail first. DON'T DO THIS!
  • I use python2 and when I open an xml and just write to another all tags change to a new tag ns0:previoustag why?
  • ns0 looks like a namespace, have a read of docs.python.org/2/library/…