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HTML Cleaning and Entity Conversion - Python
Hypertext markup language i.e. HTML is a markup language that is used to create webpages content on the internet. HTML document files may contain some unwanted or malicious elements which can cause several issues while rendering the webpage. Before processing the HTML content we need to perform HTML cleaning for removal and cleaning of the malicious elements in the file. HTML entities are special characters that need to be converted into corresponding HTML representations to ensure proper rendering in browsers. In this article, we will understand cleaning and entity conversion methods using Python.
HTML Cleaning
HTML cleaning is done to remove unwanted and malicious elements from HTML file like removing unwanted elements, such as JavaScript code, CSS styles, or potentially harmful tags, from an HTML document. This makes the content more secure and integrity of the content is retained.
HTML Cleaning using Beautiful Soup library
The beautiful Soup library can be effectively used to clean the HTML content using the find() and decompose() methods. By leveraging the find and decompose methods of Beautiful Soup, unwanted elements such as script and style tags can be easily removed from the HTML document. Additionally, Beautiful Soup allows for further customization by adding logic to remove other undesired elements based on specific requirements, ensuring a clean and sanitized HTML output.
Example
In the below above, we define a function called clean_html that takes an HTML string as input. We create a Beautiful Soup object by parsing the HTML using the 'lxml' parser. We then iterate through the document, finding and removing <script> and <style> tags. Additional logic can be added to remove other unwanted elements, such as <iframe> or <object> tags. As output, we return the cleaned HTML as a string.
from bs4 import BeautifulSoup
def clean_html(html):
soup = BeautifulSoup(html, 'lxml')
# Remove script tags
for script in soup.find_all('script'):
script.decompose()
# Remove style tags
for style in soup.find_all('style'):
style.decompose()
# Remove other unwanted elements
# ...
return str(soup)
# Example usage
html = '<html><head><script>alert("Hello, world!")</script></head><body><h1>Welcome</h1></body></html>'
cleaned_html = clean_html(html)
print(cleaned_html)
Output
<html><head></head><body><h1>Welcome</h1></body></html>
HTML cleaning using lxml library
In addition to Beautiful Soup, another powerful library for HTML cleaning in Python is lxml. It provides a built-in function called clean_html() that can remove unwanted elements and sanitize HTML documents.
Example
In the example below, we import the clean_html() function from lxml.html.clean module. We define our own clean_html() function that takes an HTML string as input and uses clean_html() to perform the cleaning operation. The function returns the cleaned HTML.
The clean_html() function in lxml performs a number of cleaning operations on the HTML document. It removes script tags, style tags, and other potentially dangerous elements. It also sanitizes the HTML by removing any invalid or improperly formatted tags or attributes. The function ensures that the resulting HTML is safe and well-formed.
from lxml.html.clean import clean_html as lxml_clean_html
def clean_my_html(html):
cleaned_html = lxml_clean_html(html)
return cleaned_html
# Example usage
html = '<html><head><script>alert("Hello, world!")</script></head><body><h1>Welcome</h1></body></html>'
cleaned_html = clean_my_html(html)
print(cleaned_html)
Output
<div><body><h1>Welcome</h1></body></div>
Entity Conversion
Entities in HTML are special characters like <, >, ", or & , that have special meanings in HTML. If we want this characters to be correctly represented in the web browser we need to convert them into their HTML entities. The html module of python can be used to perform entity conversion.
Example
In the below example, we import the html module and define a function called convert_entities that takes a text string as input. We use the html.escape() function to convert the special characters in the text into their corresponding HTML entities. The function returns the converted text.
import html
def convert_entities(text):
return html.escape(text)
# Example usage
text = '<p>Tom & Jerry</p>'
converted_text = convert_entities(text)
print(converted_text)
Output
<p> Tom & Jerry<p>
Conclusion
In this article, we discussed how HTML cleaning and entity conversion are done in web development to ensure security, integrity and proper rendering of HTML documents. HTML cleaning can be dine using Python beautiful soup library and the html module. Beautiful Soup allows us to parse HTML documents, find and remove unwanted elements, while the html module helps in converting special characters into their HTML entity representations. By utilizing these tools, developers can effectively clean and process HTML content, making it safer and more reliable for end users.
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