As of my last update in early 2023, the lxml library is a powerful and feature-rich library for processing XML and HTML in the Python language. It is built on top of the C libraries libxml2 and libxslt, which are themselves compliant with the latest XML and XSLT standards.
XML Compliance
libxml2 aims to be compliant with the following XML standards:
- XML 1.0 (Fifth Edition)
- Namespaces in XML
- XML Base
- RFC 2396 (Uniform Resource Identifiers)
HTML Compliance
For HTML, lxml uses libxml2's HTML parser which is designed to be tolerant of typical "real-world" HTML, which often does not adhere strictly to HTML standards. The parser can handle HTML as defined by the W3C specifications, including:
- HTML 4.01
- XHTML 1.0
- Partial HTML5 support
It's important to note that the HTML5 specification is vast, and libxml2 may not fully support every feature of HTML5. However, for most practical web scraping tasks, lxml's HTML parser is more than sufficient, and it can handle real-world HTML that may not be perfectly standards-compliant.
Using lxml
Here's a basic example of how to use lxml to parse an HTML document:
from lxml import html
html_content = """
<!DOCTYPE html>
<html>
<head>
<title>Test HTML</title>
</head>
<body>
<h1>Hello, World!</h1>
</body>
</html>
"""
# Parse the HTML content
tree = html.fromstring(html_content)
# Extract the text inside the <h1> tag
h1_text = tree.xpath('//h1/text()')[0]
print(h1_text) # Output: Hello, World!
Keeping Up-to-Date
Because lxml is a third-party library, whether it is compliant with the very latest standards also depends on how actively it is maintained and updated. The core libraries it depends on (libxml2 and libxslt) are also subject to the same considerations.
As web standards evolve, so too must the tools used to parse and manipulate web documents. Users of lxml should ensure they are using recent versions of the library to benefit from any updates or fixes related to standards compliance.
To install or update lxml, you can use pip:
pip install lxml # Install lxml
pip install --upgrade lxml # Upgrade to the latest version
In conclusion, lxml is generally compliant with the latest XML standards and provides reasonable support for modern HTML practices. However, for cutting-edge HTML5 features, there might be some limitations due to the underlying libxml2 library's capabilities at any given time. It is always a good idea to check the latest documentation and changelogs for lxml and libxml2 for the most current information on standards compliance.
