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

Question

Background

I am using SQLite to access a database and retrieve the desired information. I'm using ElementTree in Python version 2.6 to create an XML file with that information.

Code

import sqlite3
import xml.etree.ElementTree as ET

# NOTE: Omitted code where I acccess the database,
# pull data, and add elements to the tree

tree = ET.ElementTree(root)

# Pretty printing to Python shell for testing purposes
from xml.dom import minidom
print minidom.parseString(ET.tostring(root)).toprettyxml(indent = "   ")

#######  Here lies my problem  #######
tree.write("New_Database.xml")

Attempts

I've tried using tree.write("New_Database.xml", "utf-8") in place of the last line of code above, but it did not edit the XML's layout at all - it's still a jumbled mess.

I also decided to fiddle around and tried doing:
tree = minidom.parseString(ET.tostring(root)).toprettyxml(indent = " ")
instead of printing this to the Python shell, which gives the error AttributeError: 'unicode' object has no attribute 'write'.

Questions

When I write my tree to an XML file on the last line, is there a way to pretty print to the XML file as it does to the Python shell?

Can I use toprettyxml() here or is there a different way to do this?

Answer 1

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'))