How do I get Python's ElementTree to pretty print to an XML file?

Whatever your XML string is, you can write it to the file of your choice by opening a file for writing and writing the string to the file.

from xml.dom import minidom

xmlstr = minidom.parseString(ET.tostring(root)).toprettyxml(indent="   ")
with open("New_Database.xml", "w") as f:
    f.write(xmlstr)

There is one possible complication, especially in Python 2, which is both less strict and less sophisticated about Unicode characters in strings. If your toprettyxml method hands back a Unicode string (u"something"), then you may want to cast it to a suitable file encoding, such as UTF-8. E.g. replace the one write line with:

f.write(xmlstr.encode('utf-8'))

I found a way using straight ElementTree, but it is rather complex.

ElementTree has functions that edit the text and tail of elements, for example, element.text="text" and element.tail="tail". You have to use these in a specific way to get things to line up, so make sure you know your escape characters.

As a basic example:

I have the following file:

<?xml version='1.0' encoding='utf-8'?>
<root>
    <data version="1">
        <data>76939</data>
    </data>
    <data version="2">
        <data>266720</data>
        <newdata>3569</newdata>
    </data>
</root>

To place a third element in and keep it pretty, you need the following code:

addElement = ET.Element("data")             # Make a new element
addElement.set("version", "3")              # Set the element's attribute
addElement.tail = "\n"                      # Edit the element's tail
addElement.text = "\n\t\t"                  # Edit the element's text
newData = ET.SubElement(addElement, "data") # Make a subelement and attach it to our element
newData.tail = "\n\t"                       # Edit the subelement's tail
newData.text = "5431"                       # Edit the subelement's text
root[-1].tail = "\n\t"                      # Edit the previous element's tail, so that our new element is properly placed
root.append(addElement)                     # Add the element to the tree.

To indent the internal tags (like the internal data tag), you have to add it to the text of the parent element. If you want to indent anything after an element (usually after subelements), you put it in the tail.

This code give the following result when you write it to a file:

<?xml version='1.0' encoding='utf-8'?>
<root>
    <data version="1">
        <data>76939</data>
    </data>
    <data version="2">
        <data>266720</data>
        <newdata>3569</newdata>
    </data> <!--root[-1].tail-->
    <data version="3"> <!--addElement's text-->
        <data>5431</data> <!--newData's tail-->
    </data> <!--addElement's tail-->
</root>

As another note, if you wish to make the program uniformally use \t, you may want to parse the file as a string first, and replace all of the spaces for indentations with \t.

This code was made in Python3.7, but still works in Python2.7.

Install bs4

pip install bs4

Use this code to pretty print:

from bs4 import BeautifulSoup

x = your xml

print(BeautifulSoup(x, "xml").prettify())