Jinja2 and YAML for Jupyter

People use YAML and Jinja2 together; they're the core of Ansible. Sometimes you need a playground to figure out details of how they work. This magic provides both.

In:

%load_ext jinja_magic
%reload_ext jinja_magic

(Ignore the warning for %load_ext/%reload_ext.)

YAML

%%yaml variable parses the YAML in a cell into the named variable. If you omit variable, the YAML is parsed into the variable jinja_env; it's also then available through the history mechanism: Out[3] or _3.

In:

%%yaml
names:
- Jay
- Chris
- Pat

Out:

{'names': ['Jay', 'Chris', 'Pat']}

In:

%%jinja
{{ names }}

Out:

['Jay', 'Chris', 'Pat']

Jinja2

If you just want to try out a quick template, write %%jinja at the top of a cell. Both the contents of jinja_env and notebook variables are available. Below, we're using names from the %%yaml above, and separator from the notebook.

In:

separator = ", "

In:

%%jinja
{{ names|sort|join(separator) }}

Out:

Chris, Jay, Pat

Named templates

You may want to store Jinja2 code as a template.

• You can reuse the template later in the notebook;
• You can use Jinja2's powerful extends, import, and include mechanisms.

The template below is available under the name fancy_names. Files in the current directory are also available as templates.

In:

%%jinja_template fancy_names
{% for name in names %}
<b>{{ name }}</b><br>
{%- endfor %}

In:

%jinja --template fancy_names

Out:

<b>Jay</b><br>
<b>Chris</b><br>
<b>Pat</b><br>

Formatting

By default, the result of running a %jinja template is formatted as "pretty" text. You can choose other formats.

--latex requires MathJax to be loaded; it is by default. --code requires a recent version of IPython.

In:

%jinja --template fancy_names --html

Out:

Jay
Chris
Pat

An SVG example

From https://medium.com/@heyoka/scratch-made-svg-donut-pie-charts-in-html5-2c587e935d72. This template does math, so you may not want to follow its example.

In:

# Percent of circle to be filled
full = 60
# Percent distance from top to start
offset = 12.5

In:

%%jinja_template svg_example
<svg width="25%" height="25%" viewBox="0 0 42 42" class="donut">
  <circle class="donut-hole" cx="21" cy="21" r="15.91549430918954" fill="#fff"></circle>
  <circle class="donut-ring" cx="21" cy="21" r="15.91549430918954" fill="transparent" stroke="#d2d3d4" stroke-width="3"></circle>
  <circle class="donut-segment" cx="21" cy="21" r="15.91549430918954" fill="transparent" stroke="#ce4b99" stroke-width="3" 
    stroke-dasharray="{{ full }} {{ 100-full }}" stroke-dashoffset="{{ 25 - offset }}"></circle>
</svg>

In:

%jinja --template svg_example --svg

(There is an SVG image in the actual notebook.)