Py4XML

Author: Ankit Aggarwal (@MasterANK)

Language Used : Python

Github Link : Py4XML Github

Introduction to XML

XML stands for Extensible Markup Language, An XML file is a file which is used to store data in both computer and human readable. XML is a markup language much like HTML but was designed to store data, transport data and was designed to be self-descriptive. XML is a World Wide Web Consortium (W3C) recommendation while World Wide Web Consortium (W3C) is an organization whose mission is to lead the World Wide Web to its full potential by developing protocols and guidelines that ensure the long-term growth of the Web.

Features XML File

• XML Does Not Use Predefined Tags
• XML was designed to carry data - with focus on what data is
• XML is Extensible as XML applications will work as expected even if new data is added (or removed).

Difference between XML and HTML

HTML	XML
HTML tags are predefined tags.	XML tags are user defined tags.
HTML is not Case sensitive.	XML is Case sensitive.
HTML tags are used for displaying the data.	XML tags are used for describing the data not for displaying
HTML document size is relatively small.	XML document size is relatively large as the approach of formatting

Structure of XML File

Example File:

<bookstore>
  <book>
    <title>Everyday Italian</title>
    <author>Giada De Laurentiis</author>
    <year>2005</year>
    <price>30.00</price>
  </book>
  <book2>
    <title>Harry Potter and the Goblet of Fire</title>
    <author>J. K. Rowling</author>
    <year>2000</year>
    <price>30.00</price>
  </book2>
</bookstore>

Uses of XML:

• Used in XML AJAX: AJAX allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes. This means that it is possible to update parts of a web page, without reloading the whole page. AJAX applications might use XML to transport data

• Used in XPath: XPath stands for XML Path Language. XPath uses path expressions to select nodes or node-sets in an XML document. These path expressions look very much like the path expressions you use with traditional computer file systems.

• Used in XSL: XSL (eXtensible Stylesheet Language) is a styling language for XML.

• Used in XQuery: XQuery is a language for finding and extracting elements and attributes from XML documents. XQuery is to XML what SQL is to databases.

What is Py4XML?

Py4xml is the module created in order to interpret the XML file in python using python just like csv module which interpret CSV or pickle modules which interpret Binary files. Py4xml has the ability to read and write an .xml file. Py4xml can also convert the xml file into a csv file.

Installation

The Project file can be found on Github: Py4XML Github

Reading an XML File

Py4xml has a function called read_xml() which requires file_object as a parameter and returns an xml_reader class object which contains all the extracted data from the given xml file.

Example:

import py4xml

# The xml file to read is "xml 1.xml"
f = open("xml 1.xml","r") #Opening the file in read mode

# read_xml() function will read the file and extract the data
xml_file = py4xml.read_xml(f) # it takes file_object and return xml object

# Now with the help of multiple functions inside the xml object in xml_file we can extract the required data as shown in below example

#File Closing
f.close()

1. Getting reading the Root Element:

By accessing the root_element variable in the xml file object returned by read_xml() function. It will return the root_element

print(xml_file.root_element)
#It will return the root element

2. Getting list of all Element:

By accessing the element_stack variable in the xml file object returned by read_xml() function. It will return the element_stack

print(xml_file.element_stack)
#It will return the list of element present in the xml file

3. Getting the Dictionary of elements in xml file

By accessing the main_dict variable in the xml file object returned by read_xml() function. It will return the nested dictionary of elements where key will be elements and its value will be another dictionary where the key this time is a sub element and its value will be the value of the sub element.

Sample Structure of the nested dictionary:

{element1 : {sub_element1 : value, sub_element2 : value}, element2 : {sub_element1: value}}

print(xml_file.main_dict)
#It will return the nested dictionary of elements of structure as shown above

4. Getting the Dictionary of selected element in xml file

By accessing the find_element() function in the xml file object returned by read_xml() function. It requires one required parameter which is the element you need to find in the xml file and it will return the dictionary of the sub element of the supplied element.

print(xml_file.find_element("element"))
#It will return the dictionary of sub elements of the given element 

Reading an XML File with Attributes

Although it is not recommended but xml file can sometimes have an attribute defined in the element tag. As shown in the example below-

<messages>
  <note id="501">
    <to>Tove</to>
    <from>Jani</from>
    <heading>Reminder</heading>
    <body>Don't forget me this weekend!</body>
  </note>
  <note id="502">
    <to>Jani</to>
    <from>Tove</from>
    <heading>Re: Reminder</heading>
    <body>I will not</body>
  </note>
</messages>

in the given example, it can we concluded that id is category and is defined as <element category="Value">

While iterating over such xml files with py4xml, the structure of the main dictionary is slightly changed to accompany the category tag. The keys of the main_dict will be changed as element_value where value is the value of the category and a new sub_element will be added for category as <Category_category>Value</Category_category>

Sample New Structure of the nested dictionary:

{element1_value : {category_category1 : value, sub_element1 : value, sub_element2 : value}, element2_value : {category_category1 : value, sub_element1: value}}

Writing Dictionary in XML File

Py4xml has a function called dict_write_xml() and it has 3 required parameters. The first parameter is for the root_element which will commonly be in string format. The secound parameter is data or the elements and sub_element which should be provided in the nested dictionary format as described below. The third and last parameter is the write_f or file_object where everything is supposed to be written. This function doesn't return anything.

Sample Structure of the nested dictionary:

{element1 : {sub_element1 : value, sub_element2 : value}, element2 : {sub_element1: value}}

*Note - The file must be opened in write mode only. If you wish to append data there is another function for that.

Example:

import py4xml

root_element = "Cards" 

#Nested dictionary of Sample Data
data = {"Pika" : {"HP": 100,"Defence" : 50,"Speed": 80 }, "Snorlax":{"HP":100,"Defence":100,"Speed": 0} }

#The xml file to write is "xml 2.xml"
f = open("xml 2.xml","w") #Opening the file in write mode

# dict_write_xml() will write the data in file
dict_write_xml(root_element,data,f)

#File Closing
f.close()

Output in File:

<cards>
  <Pika>
    <HP>100</HP>
    <Defence>50</Defence>
    <Speed>80</Speed>
  </Pika>
  <Snorlax>
    <HP>100</HP>
    <Defence>100</Defence>
    <Speed>0</Speed>
  </Snorlax>
</cards>

Extending an XML File

Py4xml have a function called extend_xml() which can be used to add data to the xml file. It has two required parameters. The first parameter is data which will be in dictionary format and will contain the data that needs to be appended to the file. The secound parameter is write_f which will be the xml file where data needs to be added.

*Note: the xml file must be opened in "r+" mode only

Example:

# Data that needed to be added
data = {"Arceus":{"HP":100,"Defence":100,"Speed":100},
"Gratina":{"HP":99,"Defence":99,"Speed":99}}

#XML file to add data to and it must be opened in "r+"
write_f = open("Tests\XML 2.xml","r+")

#Calling extend_xml function
py4xml.extend_xml(data,write_f)

#File Closing
write_f.close()

Converting CSV to XML file

py4xml have a function called csv_to_xml() and it has four required parameters. This function is used to convert a csv file into an xml file. The first parameter is root_element which will accept the string to be written as root_element of the xml file. The secound parameter is csv_f which will be the csv file which will hold data that needs to be converted. The third parameter is the key which will be the column name and the value of the columns will be used for elements tag. The fourth and last parameter is xml_f and it will be the xml file in which data should be written.

*Note- The key should be unique so that two element tags would not conflict with each other. The csv file must be opened in read mode and the xml file must be opened in write mode.

Example:

csv file (File Path:Tests\csv 1.csv):

id,name,age,height,weight
1,Alice Marry,20,62,120.6
2,Freddie,21,74,190.6
3,Bob Douglas,17,68,120.0

Code-

#CSV file in read mode
csv_f = open("Tests\csv 1.csv","r")

#XML file in write mode
xml_f = open("Tests\XML 4.xml","w")

#Root_element for xml file
root_element = "Student_Data"

#"name" in csv file can be used as key as it is unique
key = "name"          

#Calling the csv to xml function
py4xml.csv_to_xml(root_element,csv_f,key,xml_f)

#File Closing
csv_f.close()
xml_f.close()

Output XML file (File Path:Tests\XML 4.xml ):

<Student_Data>
  <Alice_Marry>
    <id>1</id>
    <name>Alice Marry</name>
    <age>20</age>
    <height>62</height>
    <weight>120.6</weight>
  </Alice_Marry>
  <Freddie>
    <id>2</id>
    <name>Freddie</name>
    <age>21</age>
    <height>74</height>
    <weight>190.6</weight>
  </Freddie>
  <Bob_Douglas>
    <id>3</id>
    <name>Bob Douglas</name>
    <age>17</age>
    <height>68</height>
    <weight>120.0</weight>
  </Bob_Douglas>
</Student_Data>

Converting XML to CSV file

py4xml have a function called xml_to_csv() and it has two required parameters and one optional parameter. This function is used to convert a xml file into a csv file. The first parameter is xml_f which will be the xml file for input data. The secound parameter is csv_f in which the data should be written. The third parameter is elementcol which is optional as this will represent the column name for the element. If the column name is not given then the element tag will not be stored in the csv file.

*Note- xml file must be opened in read mode. The csv file must be opened in write mode and newline must bean empty string to avoid the empty row bug of the csv module.

Example:

XML file (File Path:Tests\XML 4.xml):

<Student_Data>
  <Alice>
    <name>Alice</name>
    <id>1</id>
    <age>20</age>
    <height>62</height>
    <weight>120.6</weight>
  </Alice>
  <Freddie>
    <name>Freddie</name>
    <id>2</id>
    <age>21</age>
    <height>74</height>
    <weight>190.6</weight>
  </Freddie>
  <Bob>
    <name>Bob</name>
    <id>3</id>
    <age>17</age>
    <height>68</height>
    <weight>120.0</weight>
  </Bob>
</Student_Data>

Code-

#XML file in read mode
xml_f = open("Tests\XML 4.xml","r")

#CSV file in write mode and newline should be empty string 
csv_f = open("Tests\csv 1.csv","w",newline="")  
             
#elementcol is column name for element tag
elementcol = "name"                             

#Calling the xml to csv function
py4xml.xml_to_csv(xml_f,csv_f,elementcol)

#File Closing
csv_f.close()
xml_f.close()

Output CSV file (File Path:Tests\csv 1.csv):

name,id,age,height,weight
Alice,1,20,62,120.6
Freddie,2,21,74,190.6
Bob,3,17,68,120.0

Demo Python File

Visit the Github repository and download the "Tests" folder and "Demo XML.py" in order to check the full demo version of the code in action

(https://github.com/MasterANK/py4xml)