cssutils CSS Parser and Manipulator

2.11.1 · active · verified Thu Apr 09

cssutils is a Python library for parsing and manipulating CSS (Cascading Style Sheets). It provides a full DOM interface for CSS stylesheets, rules, and declarations, allowing for programmatic creation, modification, and serialization of CSS. The library is currently at version 2.11.1 and sees regular maintenance releases, typically every few months.

Warnings

breaking Major API overhaul in version 2.0.0. All custom API previously found in `cssutils.css` (e.g., `cssutils.css.CSSStyleSheet`, `cssutils.css.Rule`) and other custom classes were removed. All functionality is now exclusively available through the W3C DOM interface.
Fix: Rewrite code to use the main `cssutils` module and its W3C DOM-compliant methods and objects (e.g., `cssutils.parseString()`, `cssutils.CSSStyleSheet()`). Do not use `from cssutils.css import ...`.
gotcha Default serialization (`cssText`) might not produce the exact output format expected (e.g., indentation, line breaks, specific property ordering).
Fix: Customize serialization preferences using `cssutils.ser.prefs`. For example, `cssutils.ser.prefs.indent = 4` to set indentation or `cssutils.ser.prefs.keepemptyrules = False` to remove empty rules.
gotcha cssutils uses Python's `logging` module for warnings and errors during parsing. By default, only `WARNING` and above messages might be shown, potentially masking minor parsing issues.
Fix: Configure the `cssutils.log` level to `INFO` or `DEBUG` to see more detailed parsing messages, especially during development or debugging problematic CSS. Example: `cssutils.log.setLevel(logging.INFO)`.

Install

pip install cssutils Install stable version

Imports

cssutils
```
import cssutils
```
CSSStyleSheet
```
import cssutils
sheet = cssutils.CSSStyleSheet()
```
The 'cssutils.css' module and custom classes were removed in version 2.x. All functionality is now accessed through the main `cssutils` module via the W3C DOM API.

Quickstart

This quickstart demonstrates parsing a CSS string, accessing and modifying properties within a CSS rule, and creating a new CSS stylesheet programmatically. It also shows how to serialize a `CSSStyleSheet` object back into a CSS string.

import cssutils
import logging

# Suppress cssutils logging for cleaner output in example
cssutils.log.setLevel(logging.CRITICAL)

# Parse a CSS string
sheet = cssutils.parseString('a { color: red; font-size: 16px; }')

# Accessing rules and properties
rule = sheet.cssRules[0] # Get the first rule
print(f"Selector: {rule.selectorText}") # Output: Selector: a
print(f"Color: {rule.style.color}") # Output: Color: red
print(f"Font Size: {rule.style.fontSize}") # Output: Font Size: 16px

# Modifying a rule
rule.style.color = 'blue'

# Creating a new stylesheet and adding a rule
new_sheet = cssutils.CSSStyleSheet()
new_sheet.add('p { margin: 10px; }')

# Add the modified rule from the first sheet to the new one
new_sheet.add(rule)

# Serialize the new stylesheet to a string
print('\n--- New Stylesheet ---')
print(new_sheet.cssText)

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