beautifulsoupvscssselect
beautifulsoup is a Python library for pulling data out of HTML and XML files. It creates parse trees from the source code that can be used to extract data from HTML, which is useful for web scraping. With beautifulsoup, you can search, navigate, and modify the parse tree. It sits atop popular Python parsers like lxml and html5lib, allowing users to try out different parsing strategies or trade speed for flexibility.
beautifulsoup has a number of useful methods and attributes that can be used to extract and manipulate data from an HTML or XML document. Some of the key features include:
- Searching the parse tree
You can search the parse tree using the various search methods that beautifulsoup provides, such as find(), find_all(), and select(). These methods take various arguments to search for specific tags, attributes, and text, and return a list of matching elements. - Navigating the parse tree
You can navigate the parse tree using the various navigation methods that beautifulsoup provides, such as next_sibling, previous_sibling, next_element, previous_element, parent, and children. These methods allow you to move up, down, and around the parse tree. - Modifying the parse tree
You can modify the parse tree using the various modification methods that beautifulsoup provides, such as append(), extend(), insert(), insert_before(), and insert_after(). These methods allow you to add new elements to the parse tree, or to change the position of existing elements. - Accessing tag attributes
You can access the attributes of a tag using the attrs property. This property returns a dictionary of the tag's attributes and their values. - Accessing tag text
You can access the text within a tag using the string property. This property returns the text as a string, with any leading or trailing whitespace removed.
With the above feature one can easily extract data out of HTML or XML files. It is widely used in web scraping and other data extraction projects.
It also has features for parsing XML files, special methods for dealing with HTML forms, pretty printing HTML and a few other functionalities.
cssselect is a BSD-licensed Python library to parse CSS3 selectors and translate them to XPath 1.0 expressions.
XPath 1.0 expressions can be used in lxml or another XPath engine to find the matching elements in an XML or HTML document.
cssselect is used by other popular Python packages like parsel and scrapy but can also be used on it's own to generate
valid XPath 1.0 expressions for parsing HTML and XML documents in other tools.
Note that because XPath selectors are more powerful than CSS selectors this translation is only possible one way. Converting XPath to CSS selectors is impractical and not supported by cssselect.
Highlights
Example Use
from bs4 import BeautifulSoup
# this is our HTML page:
html = """
<head>
<title>Hello World!</title>
</head>
<body>
<div id="product">
<h1>Product Title</h1>
<p>paragraph 1</p>
<p>paragraph2</p>
<span class="price">$10</span>
</div>
</body>
"""
soup = BeautifulSoup(html)
# we can iterate using dot notation:
soup.head.title
"Hello World"
# or use find method to recursively find matching elements:
soup.find(class_="price").text
"$10"
# the selected elements can be modified in place:
soup.find(class_="price").string = "$20"
# beautifulsoup also supports CSS selectors:
soup.select_one("#product .price").text
"$20"
# bs4 also contains various utility functions like HTML formatting
print(soup.prettify())
"""
<html>
<head>
<title>
Hello World!
</title>
</head>
<body>
<div id="product">
<h1>
Product Title
</h1>
<p>
paragraph 1
</p>
<p>
paragraph2
</p>
<span class="price">
$20
</span>
</div>
</body>
</html>
"""
from cssselect import GenericTranslator, SelectorError
translator = GenericTranslator()
try:
expression = translator.css_to_xpath('div.content')
print(expression)
'descendant-or-self::div[@class and contains(concat(' ', normalize-space(@class), ' '), ' content ')]'
except SelectorError as e:
print(f'Invalid selector {e}')