/jinjyaml

Application specific YAML tag of Jinja2 template

Primary LanguagePythonBSD 3-Clause "New" or "Revised" LicenseBSD-3-Clause

jinjyaml

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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.