[Tut] Parsing XML Files in Python – 4 Simple Ways

[xSicKxBot]

Parsing XML Files in Python – 4 Simple Ways

5/5 – (1 vote)

Problem Formulation and Solution Overview

This article will show you various ways to work with an

Code:

XML

file.

Code:

XML

is an acronym for Extensible Markup Language. This file type is similar to HTML. However, https://developer.mozilla.org/en-US/docs...troduction

Code:

XML

does not have pre-defined tags like HTML. Instead, a coder can define their own tags to meet specific requirements. https://developer.mozilla.org/en-US/docs...troduction

Code:

XML

is a great way to transmit and share data, either locally or via the internet. This file can be parsed based on standardized https://developer.mozilla.org/en-US/docs...troduction

Code:

XML

if structured correctly.

To make it more interesting, we have the following running scenario:

Jan, a Bookstore Owner, wants to know the top three (3) selling Books in her store. This data is currently saved in an

Code:

XML

format.

Question: How would we write code to read in and extract data from an XML file into a Python script?

We can accomplish this by performing the following steps:

• Method 1: Use
  Code:

  xmltodict()
  
  
  
• Method 2: Use
  Code:

  minidom.parse()
  
  
  
• Method 3: Use
  Code:

  etree
  
  
  
• Method 4: Use
  Code:

  untangle.parse()
  
  

Method 1: Use xmltodict()

This method uses the

Code:

xmltodict()

function to read an

Code:

XML

file, convert it to a

Code:

Dictionary

and extract the data.

In the current working directory, create an

Code:

XML

file called

Code:

books.xml

. Copy and paste the code snippet below into this file and save it.

Code:

<bookstore> <book> <title>Surrender</title> <author>Bono</author> <sales>21987</sales> </book> <book> <title>Going Rogue</title> <author>Janet Evanovich</author> <sales>15986</sales> </book> <book> <title>Triple Cross</title> <author>James Patterson</author> <sales>11311</sales> </book> </bookstore>

In the current working directory, create a Python file called

Code:

books.py

. Copy and paste the code snippet below into this file and save it. This code reads in and parses the above

Code:

XML

file. If necessary, install the

Code:

xmltodict

library.

Code:

import xmltodict with open('books.xml', 'r') as fp: books_dict = xmltodict.parse(fp.read()) fp.close() for i in books_dict: for j in books_dict[i]: for k in books_dict[i][j]: print(f'Title: {k["title"]} \t Sales: {k["sales"]}')

The first line in the above code snippet imports the

Code:

xmltodict

library. This library is needed to access and parse the

Code:

XML

file.

The following highlighted section opens

Code:

books.xml

in read mode (

Code:

r

) and saves it as a File Object, fp. If fp was output to the terminal, an object similar to the one below would display.

Code:

<_io.TextIOWrapper name='books.xml' mode='r' encoding='cp1252'>

Next, the

Code:

xmltodict.parse()

function is called and passed one (1) argument,

Code:

fp.read()

, which reads in and parses the contents of the

Code:

XML

file. The results save to

Code:

books_dict

as a

Code:

Dictionary

, and the file is closed. The contents of

Code:

books_dict

are shown below.

Code:

{'bookstore': {'book': [{'title': Surrender', 'author': 'Bono', 'sales': '21987'}, {'title': 'Going Rogue', 'author': 'Janet Evanovich', 'sales': '15986'}, {'title': 'Triple Cross', 'author': 'James Patterson', 'sales': '11311'}]}}

The final highlighted section loops through the above

Code:

Dictionary

and extracts each book’s

Code:

Title

and

Code:

Sales

.

Code:

Title: Surrender Sales: 21987 Title: Going Rogue Sales: 15986 Title: Triple Cross Sales: 11311

Note: The

Code:

\t

character represents the key on the keyboard.



Method 2: Use minidom.parse()

This method uses the

Code:

minidom.parse()

function to read and parse an XML file. This example extracts the ID, Title and Sales for each book.

This example differs from Method 1 as this

Code:

XML

file contains an additional line at the top (

Code:

<?xml version="1.0"?>

) of the file and each

Code:

<book>

tag now has an

Code:

id

(attribute) assigned to it.

In the current working directory, create an

Code:

XML

file called

Code:

books2.xml

. Copy and paste the code snippet below into this file and save it.

Code:

<?xml version="1.0"?> <bookstore> <storename>Jan's Best Sellers List</storename> <book id="21237"> <title>Surrender</title> <author>Bono</author> <sales>21987</sales> </book> <book id="21946"> <title>Going Rogue</title> <author>Janet Evanovich</author> <sales>15986</sales> </book> <book id="18241"> <title>Triple Cross</title> <author>James Patterson</author> <sales>11311</sales> </book> </bookstore>

In the current working directory, create a Python file called

Code:

books2.py

. Copy and paste the code snippet below into this file and save it.

Code:

from xml.dom import minidom doc = minidom.parse('books2.xml') name = doc.getElementsByTagName('storename')[0] books = doc.getElementsByTagName('book') for b in books: bid = b.getAttribute('id') title = b.getElementsByTagName('title')[0] sales = b.getElementsByTagName('sales')[0] print(f'{bid} {title.firstChild.data} {sales.firstChild.data}')

The first line in the above code snippet imports the

Code:

minidom

library. This allows access to various functions to parse the

Code:

XML

file and retrieve tags and attributes.

The first section of highlighted lines performs the following:

• Reads and parse the
  Code:

  books2.xml
  file and saves the results to
  Code:

  doc
  . This action creates the Object shown as (1) below.
  
  
• Retrieves the
  Code:

  <storename>
  tag and saves the results to
  Code:

  name
  . This action creates an Object shown as (2) below.
  
  
• Retrieves the
  Code:

  <book>
  tag for each
  Code:

  book
  and saves the results to
  Code:

  books
  . This action creates a List of three (3) Objects: one for each book shown as (3) below.
  

Code:

(1) <xml.dom.minidom.Document object at 0x0000022D764AFEE0> (2) <DOM Element: storename at 0x22d764f0ee0> (3) [<DOM Element: book at 0x22d764f3a30>, <DOM Element: book at 0x22d764f3c70>, <DOM Element: book at 0x22d764f3eb0>]

The last section of highlighted lines loop through the books Object and outputs the results to the terminal.

Code:

21237 Surrender 21987 21946 Going Rogue 15986 18241 Triple Cross 11311

Method 3: Use etree

This method uses

Code:

etree

to read in and parses an XML file. This example extracts the Title and Sales data for each book.

The

Code:

etree

considers the XML file as a tree structure. Each element represents a node of said tree. Accessing elements is done on an element level.

This example reads in and parses the

Code:

books2.xml

file created earlier.

Code:

import xml.etree.ElementTree as ET xml_data = ET.parse('books2.xml') root = xml_data.getroot() for books in root.findall('book'): title = books.find('title').text author = books.find('author').text sales = books.find('sales').text print(title, author, sales)

The first line in the above code snippet imports the

Code:

etree

library. This allows access to all nodes of the XML

Code:

<tag>

structure.

The following line reads in and parses

Code:

books2.xml

. The results save as an XML Object to

Code:

xml_data

. If output to the terminal, an Object similar to the one below displays.

Code:

<Element 'bookstore' at 0x000001E45E9442C0>

The following highlighted section uses a

Code:

for

loop to iterate through each

Code:

<book>

tag, extracting the

Code:

<title>

,

Code:

<author>

and

Code:

<sales>

tags for each book and outputting them to the terminal.

Code:

Surrender Bono 21987 Going Rogue Janet Evanovich 15986 Triple Cross James Patterson 11311

To retrieve the attribute of the

Code:

<book>

tag, run the following code.

This code extracts the

Code:

id

attribute from each

Code:

<book>

tag and outputs it to the terminal.

Code:

{'id': '21237'} {'id': '21946'} {'id': '18241'}

To extract the values, run the following code.

Code:

for id in root.iter('book'): vals = id.attrib.values() for v in vals: print(vals)

Code:

21237 21946 18241

Method 4: Use untangle.parse()

This method uses

Code:

untangle.parse()

to parse an XML string.

This example reads in and parses the

Code:

books3.xml

file shown below. If necessary, install the

Code:

untangle

library.

The

Code:

untangle

library converts an XML file to a Python object. This is a good option when you have a group of items, such as book names.

In the current working directory, create an

Code:

XML

file called

Code:

books3.xml

. Copy and paste the code snippet below into this file and save it. If necessary, install the

Code:

untangle

library.

Code:

<?xml version="1.0"?> <root> <book name="Surrender"/> <book name="Going Rogue"/> <book name="Triple Cross"/> </root>

In the current working directory, create a Python file called

Code:

books3.py

. Copy and paste the code snippet below into this file and save it.

Code:

import untangle book_obj = untangle.parse('books3.xml') books = ','.join([book['name'] for book in book_obj.root.book]) for b in books.split(','): print(b)

The first line in the above code snippet imports the

Code:

untangle

library allowing access to the

Code:

XML

file structure.

The following line reads in and parses the

Code:

books3.xml

file. The results save to

Code:

book_obj

.

The next line calls the

Code:

join()

function and passes it one (1) argument: List Comprehension. This code iterates through and retrieves the name of each book and saves the results to

Code:

books

. If output to the terminal, the following displays:

Code:

Surrender,Going Rogue,Triple Cross

The next line instantiates a

Code:

for

loop, iterates through each book name, and sends it to the terminal.

Code:

Surrender Going Rogue Triple Cross

Summary

This article has shown four (4) ways to work with

Code:

XML

files to select the best fit for your coding requirements.

Good Luck & Happy Coding!

Programmer Humor – Blockchain

[i]“Blockchains are like grappling hooks, in that it’s extremely cool when you encounter a problem for which they’re the right solution, but it happens way too rarely in real life.” source – xkcd[/i]