Plugins

Beginning with version 3.0, Pelican supports plugins. Plugins are a way to add features to Pelican without having to directly modify the Pelican core.

Pelican is shipped with a set of bundled plugins, but you can easily implement your own. This page describes how to use and create plugins.

How to use plugins

To load plugins, you have to specify them in your settings file. There are two ways to do so. The first method is to specify strings with the path to the callables:

PLUGINS = ['pelican.plugins.gravatar',]

Alternatively, another method is to import them and add them to the list:

from pelican.plugins import gravatar
PLUGINS = [gravatar,]

If your plugins are not in an importable path, you can specify a PLUGIN_PATH in the settings:

PLUGIN_PATH = "plugins"
PLUGINS = ["list", "of", "plugins"]

How to create plugins

Plugins are based on the concept of signals. Pelican sends signals, and plugins subscribe to those signals. The list of signals are defined in a subsequent section.

The only rule to follow for plugins is to define a register callable, in which you map the signals to your plugin logic. Let’s take a simple example:

from pelican import signals

def test(sender):
    print "%s initialized !!" % sender

def register():
    signals.initialized.connect(test)

List of signals

Here is the list of currently implemented signals:

Signal Arguments Description
initialized pelican object  
finalized pelican object invoked after all the generators are executed and just before pelican exits usefull for custom post processing actions, such as: - minifying js/css assets. - notify/ping search engines with an updated sitemap.
generator_init generator invoked in the Generator.__init__
article_generate_context article_generator, metadata  
article_generate_preread article_generator invoked before a article is read in ArticlesGenerator.generate_context; use if code needs to do something before every article is parsed
article_generator_init article_generator invoked in the ArticlesGenerator.__init__
article_generator_finalized article_generator invoked at the end of ArticlesGenerator.generate_context
get_generators generators invoked in Pelican.get_generator_classes, can return a Generator, or several generator in a tuple or in a list.
pages_generate_context pages_generator, metadata  
pages_generator_init pages_generator invoked in the PagesGenerator.__init__

The list is currently small, so don’t hesitate to add signals and make a pull request if you need them!

Note

The signal content_object_init can send a different type of object as the argument. If you want to register only one type of object then you will need to specify the sender when you are connecting to the signal.

from pelican import signals
from pelican import contents

def test(sender, instance):
        print "%s : %s content initialized !!" % (sender, instance)

def register():
        signals.content_object_init.connect(test, sender=contents.Article)

List of plugins

The following plugins are currently included with Pelican under pelican.plugins:

Ideas for plugins that haven’t been written yet:

  • Tag cloud
  • Translation

Plugin descriptions

Asset management

This plugin allows you to use the Webassets module to manage assets such as CSS and JS files. The module must first be installed:

pip install webassets

The Webassets module allows you to perform a number of useful asset management functions, including:

  • CSS minifier (cssmin, yuicompressor, ...)
  • CSS compiler (less, sass, ...)
  • JS minifier (uglifyjs, yuicompressor, closure, ...)

Others filters include gzip compression, integration of images in CSS via data URIs, and more. Webassets can also append a version identifier to your asset URL to convince browsers to download new versions of your assets when you use far-future expires headers. Please refer to the Webassets documentation for more information.

When used with Pelican, Webassets is configured to process assets in the OUTPUT_PATH/theme directory. You can use Webassets in your templates by including one or more template tags. The Jinja variable {{ ASSET_URL }} can be used in templates and is relative to the theme/ url. The {{ ASSET_URL }} variable should be used in conjunction with the {{ SITEURL }} variable in order to generate URLs properly. For example:

{% assets filters="cssmin", output="css/style.min.css", "css/inuit.css", "css/pygment-monokai.css", "css/main.css" %}
    <link rel="stylesheet" href="{{ SITEURL }}/{{ ASSET_URL }}">
{% endassets %}

... will produce a minified css file with a version identifier that looks like:

<link href="http://{SITEURL}/theme/css/style.min.css?b3a7c807" rel="stylesheet">

These filters can be combined. Here is an example that uses the SASS compiler and minifies the output:

{% assets filters="sass,cssmin", output="css/style.min.css", "css/style.scss" %}
    <link rel="stylesheet" href="{{ SITEURL }}/{{ ASSET_URL }}">
{% endassets %}

Another example for Javascript:

{% assets filters="uglifyjs,gzip", output="js/packed.js", "js/jquery.js", "js/base.js", "js/widgets.js" %}
    <script src="{{ SITEURL }}/{{ ASSET_URL }}"></script>
{% endassets %}

The above will produce a minified and gzipped JS file:

<script src="http://{SITEURL}/theme/js/packed.js?00703b9d"></script>

Pelican’s debug mode is propagated to Webassets to disable asset packaging and instead work with the uncompressed assets. However, this also means that the LESS and SASS files are not compiled. This should be fixed in a future version of Webassets (cf. the related bug report).

GitHub activity

This plugin makes use of the feedparser library that you’ll need to install.

Set the GITHUB_ACTIVITY_FEED parameter to your GitHub activity feed. For example, to track Pelican project activity, the setting would be:

GITHUB_ACTIVITY_FEED = 'https://github.com/getpelican.atom'

On the template side, you just have to iterate over the github_activity variable, as in this example:

{% if GITHUB_ACTIVITY_FEED %}
   <div class="social">
           <h2>Github Activity</h2>
           <ul>

           {% for entry in github_activity %}
               <li><b>{{ entry[0] }}</b><br /> {{ entry[1] }}</li>
           {% endfor %}
           </ul>
   </div><!-- /.github_activity -->
{% endif %}

github_activity is a list of lists. The first element is the title, and the second element is the raw HTML from GitHub.

Global license

This plugin allows you to define a LICENSE setting and adds the contents of that license variable to the article’s context, making that variable available to use from within your theme’s templates.

Gravatar

This plugin assigns the author_gravatar variable to the Gravatar URL and makes the variable available within the article’s context. You can add AUTHOR_EMAIL to your settings file to define the default author’s email address. Obviously, that email address must be associated with a Gravatar account.

Alternatively, you can provide an email address from within article metadata:

If the email address is defined via at least one of the two methods above, the author_gravatar variable is added to the article’s context.

Gzip cache

Certain web servers (e.g., Nginx) can use a static cache of gzip-compressed files to prevent the server from compressing files during an HTTP call. Since compression occurs at another time, these compressed files can be compressed at a higher compression level for increased optimization.

The gzip_cache plugin compresses all common text type files into a .gz file within the same directory as the original file.

HTML tags for reStructuredText

This plugin allows you to use HTML tags from within reST documents. Following is a usage example, which is in this case a contact form:

.. html::

    <form method="GET" action="mailto:some email">
      <p>
        <input type="text" placeholder="Subject" name="subject">
        <br />
        <textarea name="body" placeholder="Message">
        </textarea>
        <br />
        <input type="reset"><input type="submit">
      </p>
    </form>

Sitemap

The sitemap plugin generates plain-text or XML sitemaps. You can use the SITEMAP variable in your settings file to configure the behavior of the plugin.

The SITEMAP variable must be a Python dictionary and can contain three keys:

  • format, which sets the output format of the plugin (xml or txt)

  • priorities, which is a dictionary with three keys:

    • articles, the priority for the URLs of the articles and their translations

    • pages, the priority for the URLs of the static pages

    • indexes, the priority for the URLs of the index pages, such as tags,

      author pages, categories indexes, archives, etc...

    All the values of this dictionary must be decimal numbers between 0 and 1.

  • changefreqs, which is a dictionary with three items:

    • articles, the update frequency of the articles
    • pages, the update frequency of the pages
    • indexes, the update frequency of the index pages

    Valid frequency values are always, hourly, daily, weekly, monthly, yearly and never.

If a key is missing or a value is incorrect, it will be replaced with the default value.

The sitemap is saved in <output_path>/sitemap.<format>.

Note

priorities and changefreqs are information for search engines. They are only used in the XML sitemaps. For more information: <http://www.sitemaps.org/protocol.html#xmlTagDefinitions>

Example

Here is an example configuration (it’s also the default settings):

PLUGINS=['pelican.plugins.sitemap',]

SITEMAP = {
    'format': 'xml',
    'priorities': {
        'articles': 0.5,
        'indexes': 0.5,
        'pages': 0.5
    },
    'changefreqs': {
        'articles': 'monthly',
        'indexes': 'daily',
        'pages': 'monthly'
    }
}
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