Table of contents
1.
Introduction
2.
Getting Started
3.
Key Concepts
3.1.
1. HTMLParser Class:
3.2.
2. Methods and Overriding:
4.
Dive into the Code
4.1.
Basic Usage
4.2.
Extracting Attributes
4.3.
Handling Comments
5.
Practical Application
6.
Frequently Asked Questions
6.1.
Can Python’s HTML parser handle broken HTML?
6.2.
Is Python’s HTML parser suitable for large-scale web scraping?
6.3.
Can I use this parser for XML documents?
7.
Conclusion
Last Updated: Mar 27, 2024
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Python HTML Parser

Author Lekhika
1 upvote

Introduction

Web scraping is a technique used to extract data from web pages. While there are many tools and libraries in Python for this purpose, Python's built-in HTML Parser, a part of the html.parser module, is a versatile choice. This article will guide you through the wonders of the Python HTML Parser, helping you tap into the potential of web data without the weight of external dependencies.

Python HTML Parser

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Getting Started

Python’s built-in HTML parser is part of the standard library, so there's no need to install external packages. You can start using it right away.

Key Concepts

1. HTMLParser Class:

The html.parser module offers the HTMLParser class, which allows us to create custom subclasses to handle parsed data.

2. Methods and Overriding:

By overriding the built-in methods of HTMLParser, you can define custom behavior for different parsing events.

Dive into the Code

Basic Usage

Let's begin by creating a simple subclass of HTMLParser that extracts data from HTML tags:

from html.parser import HTMLParser
class MyHTMLParser(HTMLParser):
    def handle_starttag(self, tag, attrs):
        print(f"Encountered a start tag: {tag}")


    def handle_endtag(self, tag):
        print(f"Encountered an end tag: {tag}")


    def handle_data(self, data):
        print(f"Encountered some data: {data}")


# instantiate the parser and feed it some HTML
parser = MyHTMLParser()
parser.feed('<html><head><title>Python Rocks</title></head></html>')
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When you run the above code, the parser processes the HTML string, triggering our custom-defined methods and printing out the parsed data.

Extracting Attributes

You might be interested in fetching attributes like 'href' from anchor tags. Here's how you can achieve that:

def handle_starttag(self, tag, attrs):
    if tag == 'a':
        for attr in attrs:
            if attr[0] == 'href':
                print(f"Found a link: {attr[1]}")
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Handling Comments

You can also manage HTML comments by overriding the handle_comment method:

def handle_comment(self, data):
    print(f"Encountered comment: {data}")
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Practical Application

Imagine you want to fetch all headlines from a news webpage. With the HTML Parser, you can navigate through the page's structure and extract relevant details.

from html.parser import HTMLParser  # Import HTMLParser from correct module


class NewsParser(HTMLParser):
    def __init__(self):
        super().__init__()
        self.in_title_tag = False
        self.headlines = []

    def handle_starttag(self, tag, attrs):
        if tag == 'h1':
            self.in_title_tag = True

    def handle_data(self, data):
        if self.in_title_tag:
            self.headlines.append(data)

    def handle_endtag(self, tag):
        if tag == 'h1':
            self.in_title_tag = False


# Imagine the below string is a simplified version of a news webpage
html_content = """
<h1>Breaking: Python becomes the most popular language</h1>
<p>Some content here...</p>
<h1>Coding Ninjas is best</h1>
"""

parser = NewsParser()
parser.feed(html_content)
print(parser.headlines)
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Output:

Output

Frequently Asked Questions

Can Python’s HTML parser handle broken HTML?

It tries its best, but for heavily malformed HTML, using libraries like Beautiful Soup or lxml with robust parsers might be better.

Is Python’s HTML parser suitable for large-scale web scraping?

While it's lightweight and easy to use, for large-scale scraping or when needing advanced functionalities, specialized libraries like Scrapy are recommended.

Can I use this parser for XML documents?

While primarily for HTML, it can parse XML to an extent. For robust XML parsing, consider using the xml module in Python's standard library.

Conclusion

Python's built-in HTML Parser is a light, easy-to-use tool for basic web scraping tasks. While not as feature-rich as some external libraries, it offers a quick, dependency-free way to extract data from web pages. Whether you're stepping into web scraping or need a simple tool for a small project, the HTML parser might just be your perfect companion. Happy parsing!

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