Pynliner

0.8.0 · maintenance · verified Thu Apr 16

Pynliner is a Python library that converts CSS styles in an HTML document to inline styles, primarily designed for crafting HTML emails to ensure consistent rendering across various email clients. It leverages BeautifulSoup for HTML parsing and cssutils for CSS processing. The current stable version is 0.8.0, released in 2019, indicating an infrequent release cadence and a current state of maintenance rather than active development.

Common errors

```
cssutils.css.CSSSyntaxError: [err] ... (e.g., 'Expected semicolon or '}', got 'invalid_token')
```
cause The input CSS contains syntax errors, which cssutils (Pynliner's underlying CSS parser) cannot process.

fix Review and validate your CSS syntax. Use a CSS linter or validator to identify and correct any malformed rules or properties before passing the HTML to Pynliner.
```
AttributeError: 'NoneType' object has no attribute 'find_all' (or similar BeautifulSoup errors like 'NoneType' object has no attribute 'select')
```
cause This error typically occurs when Pynliner's internal BeautifulSoup parsing cannot find an expected HTML element, and subsequent operations are attempted on a 'None' object. This can happen with malformed HTML or incorrect CSS selectors used internally by Pynliner if the HTML structure is very unusual.

fix Ensure your HTML is well-formed and valid. Check for unclosed tags, incorrect nesting, or other structural issues that might confuse the HTML parser.
```
Pynliner output does not include expected styles (styles are missing or incorrect in the output HTML).
```
cause The most common causes are using external CSS files (<link>), @import rules, or very complex/modern CSS selectors that Pynliner's older version might not fully support or correctly resolve against the HTML.

fix Verify that all CSS is embedded in <style> tags. Avoid @import. Simplify complex CSS selectors if possible. Remember Pynliner processes styles in order, so later rules might override earlier ones based on specificity and document order.

Warnings

gotcha Pynliner only processes CSS found within <style> blocks and existing 'style' attributes in the HTML string. It explicitly ignores external CSS files linked via <link rel="stylesheet"> tags.
Fix: Ensure all CSS intended for inlining is embedded directly within <style> tags in the HTML document's <head> section.
gotcha Pynliner does not resolve CSS @import rules within <style> blocks. Any styles imported this way will not be processed or inlined.
Fix: Consolidate all CSS into a single <style> block, avoiding @import rules for external stylesheets.
gotcha The library's last release was in 2019 (v0.8.0), and development appears dormant. It may not fully support modern CSS features (e.g., Flexbox, Grid, advanced pseudo-selectors) or newer HTML5 structures, potentially leading to incomplete or incorrect inlining for contemporary web designs.
Fix: Test thoroughly with target email clients. For cutting-edge CSS, consider alternative, more actively maintained tools or simplify designs to what's well-supported by email clients.
gotcha Pynliner respects CSS specificity rules. If a style is defined with `!important` in a <style> block, it will override an existing inline style or a less specific rule, which can lead to unexpected results if not carefully managed.
Fix: Carefully manage CSS specificity and the use of `!important`. Test the output to ensure styles are applied as intended, especially when combining authored CSS with existing inline styles.

Install

pip install pynliner Install Pynliner

Imports

Pynliner
```
from pynliner import Pynliner
```

Quickstart

Initialize Pynliner and apply CSS styles from an HTML string into inline 'style' attributes. This is the primary method for inlining CSS for email clients.

from pynliner import Pynliner

html_content = """
<html>
<head>
    <style type="text/css">
        h1 { color: red; }
        p { font-size: 16px; margin: 0; }
        .container { background-color: #f0f0f0; padding: 20px; }
    </style>
</head>
<body>
    <div class="container">
        <h1>Hello, Pynliner!</h1>
        <p>This is a paragraph with inlined styles.</p>
    </div>
</body>
</html>
"""

inliner = Pynliner()
inlined_html = inliner.from_string(html_content)

# The inlined_html string now contains the HTML with CSS styles moved inline.
# print(inlined_html)

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