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Pelican is a Python-powered static blog generator that processes ReStructuredText and Markdown articles and pages and converts them to HTML. I use Pelican to power this blog.

There is a YouTube RST directive built in to Pelican core but it really shouldn’t exist there.

I submitted a pull request for Pelican core to enable Vimeo videos in articles but that request was declined because it didn’t belong in the core. So I decided I would write it as a plugin instead and while I was doing it, also wrote a plugin for YouTube so that it could be removed from the core.

There is a decent amount of detail in the Pelican documentation on how to write plugins, I’m not going to cover the whole process but I thought I would cover a little of what I did.

Adding an RST directive

Really all we’re doing is modifying docutils on-the-fly to tell it how to understand new directives, so we need to import directives from docutils

from docutils.parsers.rst import directives, Directive

With this in place, we can dynamically register a new directive to docutils

directives.register_directive('vimeo', Vimeo)

The first argument we pass in is the name of our directive, the second argument is the name of the class we wish to be invoked.

Writing the Directive

I’ll now break down the Vimeo class and explain what it does, piece by piece.

We will need to import an extra method from docutils

from docutils import nodes

This is used to append segments of data together, in our case HTML.

class Vimeo

class Vimeo(Directive):

This is pretty self explanatory, we define a new class that inherits from docutils.parsers.rst.Directive.

Next we define a method for handling our alignment choices

def align(argument):
    return directives.choice(argument, ('left', 'center', 'right'))

Now we need to set some base values against our class for docutils to know how many arguments are required and so on, it’s pretty easy to understand. For the alignment option we pass it the callable method declared above, but without calling it.

required_arguments = 1
optional_arguments = 2
option_spec = {
    'width': directives.positive_int,
    'height': directives.positive_int,
    'align': align
}

final_argument_whitespace = False
has_content = False

And finally we move on to the meat of the plugin, the method that actually does the processing.

The method name is called run because that is required by docutils.

def run(self):

First I get the videoID from the first argument in the RST, I tend set default values for width, height and alignment. Those three arguments are optional, but if they have been defined then I override the defaults.

videoID = self.arguments[0].strip()
width = 420
height = 315
align = 'left'

if 'width' in self.options:
    width = self.options['width']

if 'height' in self.options:
    height = self.options['height']

if 'align' in self.options:
    align = self.options['align']

Next I define the Vimeo URL and the two blocks of HTML that create the surrounding div element and the video iframe. Here I also replace the videoID in to the URL and also the optional arguments specified above.

url = 'https://player.vimeo.com/video/{}'.format(videoID)
div_block = '<div class="vimeo" align="{}">'.format(align)
embed_block = '<iframe width="{}" height="{}" src="{}" '\
              'frameborder="0"></iframe>'.format(width, height, url)

And finally I create a list of docutils nodes with the HTML we created above.

return [
    nodes.raw('', div_block, format='html'),
    nodes.raw('', embed_block, format='html'),
    nodes.raw('', '</div>', format='html')]

And that’s really it, it’s a simple as that. You can view full source on GitHub and also read the manual for pelican-vimeo on it’s software page on this website.

Kura

Anarchist. Pessimist. Bipolar. Hacker. Hyperpolyglot. Musician. Ex pro gamer. Cunt. They/Them.

Kura

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