jinjyaml

Application specific tag of Jinja2 template in PyYAML.

It may be useful if you only want to render special tag nodes in the document, instead of whole YAML string as a template.

Usage

Example 1

1. Add Jinja2 template constructor for tag "!j2"

   import yaml
   import jinjyaml as jy
   
   ctor = jy.Constructor()
   yaml.add_constructor("!j2", ctor, yaml.SafeLoader)

2. create YAML file 1.yml, with such contents:

   array: !j2 |
     {% for i in range(n) %}
     - sub{{i}}: {{loop.index}}
     {% endfor %}

3. load and render the YAML file

   with open("1.yml") as fp:
       data = yaml.load(fp, Loader=yaml.SafeLoader)
       # or for the short:
       # data = yaml.safe_load(fp)
   
   jy.extract(data, context={"n": 3}, inplace=True)
   
   print(data)

We'll get:

{"array": [{"sub0": 1}, {"sub1": 2}, {"sub2": 3}]}

Example 2

We have such YAML files:

• sub-1.yml:

  "1.1": one
  "1.2": two

• sub-2.yml:

  "2.1":
    "2.1.1": three
    "2.1.2": four

• main.yml:

  foo: !j2 |
  
    {% filter indent %}
    {% include "sub-1.yml" %}
    {% endfilter %}
  
    {% filter indent %}
    {% include "sub-2.yml" %}
    {% endfilter %}

execute python code:

from pprint import pprint

import jinja2
import jinjyaml as jy
import yaml

env = jinja2.Environment(loader=jinja2.FileSystemLoader("."))

ctor = jy.Constructor()
yaml.add_constructor("!j2", ctor, yaml.SafeLoader)

with open("main.yml") as fp:
    doc = yaml.safe_load(fp)

obj = jy.extract(doc, env)
pprint(obj)

We'll get:

{"foo": {"1.1": "one",
         "1.2": "two",
         "2.1": {"2.1.1": "three", "2.1.2": "four"}}}

NOTE:

Since Jinja2's include and indent do not work very nice with indention languages like Python or YAML, it's not advised to use the feature in a complex case.