Django, Flatpages, Markdown, and Syntax Highlighting

For what should have been an easy task, this turned out to be extraordinarily difficult.

I assume you have Django already installed. If not, the tutorials on djangoproject.com aren’t too terrible, provided you’re not on a shared server (that’s another story!). I’m using Flatpages, but you can use whatever you want to follow along with this tutorial.

1. Install Markdown and Pygments for Python if you haven’t already. If you’re on Ubuntu, you can `sudo apt-get install python-markdown` or `easy_install Markdown` and `sudo apt-get install python-pygments`.

2. Go into your Django app and `mkdir templatetags`. This should be at the same level as `manage.py`, `settings.py` and `urls.py`. Then `cd` into that directory, and `touch __init__.py` (so that it becomes a module) and then add another file called something like `tags.py` (don’t name it “markdown.py” — that’ll bite you later). Paste this code in there:

from django import template
from django.template.defaultfilters import stringfilter

from django.conf import settings

register = template.Library()

@register.filter(name='markdown')
@stringfilter
def markdown(value, arg=''):
    """
    Filter to create HTML out of Markdown, using custom extensions.

    The diffrence between this filter and the django-internal markdown
    filter (located in ``django/contrib/markup/templatetags/markup.py``)
    is that this filter enables extensions to be load.

    Usage::

        {{ object.text|markdown }}
        {{ object.text|markdown:"save" }}
        {{ object.text|markdown:"codehilite" }}
        {{ object.text|markdown:"save,codehilite" }}

    This code is taken from
    http://www.freewisdom.org/projects/python-markdown/Django
    """

    try:
        import markdown
    except ImportError:
        if settings.DEBUG:
            raise (template.TemplateSyntaxError,
                   "Error in {% markdown %} filter: "
                   + "The markdown library isn't installed.")
        else :
            from django.utils.html import escape, linebreaks
            return linebreaks(escape(value))
    else:
        extensions=arg.split(",")
        if len(extensions) > 0 and extensions[0] == "safe" :
            extensions = extensions[1:]
            safe_mode = True
        else :
            safe_mode = False
        return markdown.markdown(value, extensions, safe_mode=safe_mode)

Yes, I’m leaving the link in there; I didn’t write that code.

3. Go into `settings.py` and add your app to the `INSTALLED_APPS`. You actually have to `import` your own app too; this baffled me for about an hour. My app is called `tech_eval` so my `INSTALLED_APPS` looks like this:

import tech_eval # you can put this line at the top of settings.py if you want

INSTALLED_APPS = (
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.sites',
    'django.contrib.admin',
    'django.contrib.flatpages',
    'tech_eval',
)

4. Like I said, I’m using Flatpages, so my template looks like this (I saved it to djangoproject/app/templates/flatpages/default.html).

{% load tags %}
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
    <title>{{ flatpage.title }}</title>
    <link rel="stylesheet" type="text/css" href="/tech_eval/media/css/code_style.css" />
</head>
<body>
    <h1>{{ flatpage.title }}</h1>
    {{ flatpage.content|markdown:"codehilite"|safe}}
</body>
</html>

Notice how we filter the content with markdown, make sure the codehilite extension is used, and flag it as `safe` afterwords (otherwise Django will automatically character-encode everything).

5. Hopefully this is already working for you at this point, but you probably want to add some color to your code. You can generate the appropriate css file with this:

pygmentize -f html -S default -a .codehilite >> code_style.css

Some different styles you can use (at least on my system) are:

['manni', 'colorful', 'murphy', 'autumn', 'bw', 'pastie', 'native', 'perldoc', 'borland', 'trac', 'default', 'fruity', 'emacs', 'friendly']

(stolen from here).

Or just copy and paste this CSS file if you’re lazy:

.codehilite .c { color: #408080; font-style: italic } /* Comment */
.codehilite .err { border: 1px solid #FF0000 } /* Error */
.codehilite .k { color: #008000; font-weight: bold } /* Keyword */
.codehilite .o { color: #666666 } /* Operator */
.codehilite .cm { color: #408080; font-style: italic } /* Comment.Multiline */
.codehilite .cp { color: #BC7A00 } /* Comment.Preproc */
.codehilite .c1 { color: #408080; font-style: italic } /* Comment.Single */
.codehilite .cs { color: #408080; font-style: italic } /* Comment.Special */
.codehilite .gd { color: #A00000 } /* Generic.Deleted */
.codehilite .ge { font-style: italic } /* Generic.Emph */
.codehilite .gr { color: #FF0000 } /* Generic.Error */
.codehilite .gh { color: #000080; font-weight: bold } /* Generic.Heading */
.codehilite .gi { color: #00A000 } /* Generic.Inserted */
.codehilite .go { color: #808080 } /* Generic.Output */
.codehilite .gp { color: #000080; font-weight: bold } /* Generic.Prompt */
.codehilite .gs { font-weight: bold } /* Generic.Strong */
.codehilite .gu { color: #800080; font-weight: bold } /* Generic.Subheading */
.codehilite .gt { color: #0040D0 } /* Generic.Traceback */
.codehilite .kc { color: #008000; font-weight: bold } /* Keyword.Constant */
.codehilite .kd { color: #008000; font-weight: bold } /* Keyword.Declaration */
.codehilite .kp { color: #008000 } /* Keyword.Pseudo */
.codehilite .kr { color: #008000; font-weight: bold } /* Keyword.Reserved */
.codehilite .kt { color: #B00040 } /* Keyword.Type */
.codehilite .m { color: #666666 } /* Literal.Number */
.codehilite .s { color: #BA2121 } /* Literal.String */
.codehilite .na { color: #7D9029 } /* Name.Attribute */
.codehilite .nb { color: #008000 } /* Name.Builtin */
.codehilite .nc { color: #0000FF; font-weight: bold } /* Name.Class */
.codehilite .no { color: #880000 } /* Name.Constant */
.codehilite .nd { color: #AA22FF } /* Name.Decorator */
.codehilite .ni { color: #999999; font-weight: bold } /* Name.Entity */
.codehilite .ne { color: #D2413A; font-weight: bold } /* Name.Exception */
.codehilite .nf { color: #0000FF } /* Name.Function */
.codehilite .nl { color: #A0A000 } /* Name.Label */
.codehilite .nn { color: #0000FF; font-weight: bold } /* Name.Namespace */
.codehilite .nt { color: #008000; font-weight: bold } /* Name.Tag */
.codehilite .nv { color: #19177C } /* Name.Variable */
.codehilite .ow { color: #AA22FF; font-weight: bold } /* Operator.Word */
.codehilite .w { color: #bbbbbb } /* Text.Whitespace */
.codehilite .mf { color: #666666 } /* Literal.Number.Float */
.codehilite .mh { color: #666666 } /* Literal.Number.Hex */
.codehilite .mi { color: #666666 } /* Literal.Number.Integer */
.codehilite .mo { color: #666666 } /* Literal.Number.Oct */
.codehilite .sb { color: #BA2121 } /* Literal.String.Backtick */
.codehilite .sc { color: #BA2121 } /* Literal.String.Char */
.codehilite .sd { color: #BA2121; font-style: italic } /* Literal.String.Doc */
.codehilite .s2 { color: #BA2121 } /* Literal.String.Double */
.codehilite .se { color: #BB6622; font-weight: bold } /* Literal.String.Escape */
.codehilite .sh { color: #BA2121 } /* Literal.String.Heredoc */
.codehilite .si { color: #BB6688; font-weight: bold } /* Literal.String.Interpol */
.codehilite .sx { color: #008000 } /* Literal.String.Other */
.codehilite .sr { color: #BB6688 } /* Literal.String.Regex */
.codehilite .s1 { color: #BA2121 } /* Literal.String.Single */
.codehilite .ss { color: #19177C } /* Literal.String.Symbol */
.codehilite .bp { color: #008000 } /* Name.Builtin.Pseudo */
.codehilite .vc { color: #19177C } /* Name.Variable.Class */
.codehilite .vg { color: #19177C } /* Name.Variable.Global */
.codehilite .vi { color: #19177C } /* Name.Variable.Instance */
.codehilite .il { color: #666666 } /* Literal.Number.Integer.Long */
.codehilitetable { border: 1px solid #666; width: 100%; background-color: #666; }
.codehilitetable .linenos { background-color: #666; padding: 0 5px; width: 20px; }
.codehilitetable .code { padding: 0 15px; background-color: #fff; }

And that should pretty much be it. Let me know if I missed anything or this was too difficult to follow along.

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