Minimal Python Template

template.py

#!/usr/bin/env python3
# Taken from:
#   string as file: http://stackoverflow.com/a/142251
#   yaml !include: http://stackoverflow.com/a/9577670

import sys
import os.path
import yaml
import jinja2
import io
from os import path

class Loader(yaml.Loader):

    def __init__(self, stream, fname=''):

        if fname == '':
            self._root = os.path.split(stream.name)[0]
        else:
            self._root = fname

        super(Loader, self).__init__(stream)

    def include(self, node):

        filename = os.path.join(self._root, self.construct_scalar(node))
        extension = os.path.splitext(filename)[1].lstrip('.')

        with open(filename, 'r') as f:
            if extension in ('yaml', 'yml'):
                return yaml.load(f, Loader)
            else:
                return ''.join(f.readlines())

def _new_jinja_env(tpl_path):
    loader = jinja2.loaders.FileSystemLoader(tpl_path)
    env = jinja2.Environment(loader=loader)
    return env

def main(argv):

    tpl_file_path = argv[0]
    tpl_path, tpl_fname = path.split(tpl_file_path)

    # First load the data and resolve jinja2 from environment
    env = _new_jinja_env(tpl_path)
    tpl = env.get_template(tpl_fname)
    data = tpl.render(env=os.environ)


    with io.StringIO() as f:
        f.write(data)
        f.name = tpl_file_path
        f.seek(0)

        # Now load yaml data and parse includes
        Loader.add_constructor('!include', Loader.include)
        data = yaml.load(f, Loader)

    # Now output to stdout
    output = yaml.safe_dump(data, default_flow_style=False)

    print(output)

if __name__ == "__main__":
    main(sys.argv[1:])