starter-python3/main.py

#! /usr/bin/env python3

import sys

import argparse
import jinja2
import pydantic
import yaml


def to_yaml(value):
    value_str = yaml.safe_dump(value, default_style='"', default_flow_style=True)
    return value_str[:-1] if value_str and value_str[-1] == '\n' else value_str


class ConfigBase(pydantic.BaseModel):
    pass


class ConfigRoot(ConfigBase):
    answer: str = pydantic.Field()


class Options(pydantic.BaseModel):
    config_path: str = pydantic.Field(alias='config')


def main(argv):
    default_options = Options(**{
        'config': './config.yml'
    })

    parser = argparse.ArgumentParser(description='Some awesome project')
    parser.add_argument('-c', '--config', type=str, default=default_options.config_path, help='Path to config file')
    args = parser.parse_args(argv[1:])

    options = Options(**vars(args))

    with open(options.config_path, 'r') as f:
        config_template = f.read()

    jinja_env = jinja2.Environment(
        loader=jinja2.PrefixLoader({
            'config': jinja2.DictLoader({
                'config.yml': config_template
            }),
            'config.d': jinja2.FileSystemLoader('{}.d'.format(options.config_path))
        }),
        extensions=["jinja2.ext.do"]
    )
    jinja_env.filters['yaml'] = to_yaml

    template = jinja_env.get_template('config/config.yml')
    config_yml = template.render(options=options)
    config_dict = yaml.safe_load(config_yml)
    config = ConfigRoot(**config_dict)

    print(options.config_path)
    print(config.answer)

    return 0


if __name__ == '__main__':
    sys.exit(main(sys.argv))