Jinja2 - Config Template

gen_config.py

import argparse
import errno
import os
import sys

from jinja2 import Environment, FileSystemLoader, StrictUndefined

UTF8 = 'utf8'
TEMPLATE = 'template'


def parse_option(sys_args):
    parser = argparse.ArgumentParser(
        description='Generate a configuration combining templates',
        formatter_class=argparse.RawTextHelpFormatter
    )

    parser.add_argument('--input_folder', '-i', required=True, help='Input folder')
    parser.add_argument('--output_folder', '-o', required=True, help='Output folder')

    return parser, parser.parse_args(sys_args)


def create_directory(filename):
    try:
        os.makedirs(os.path.dirname(filename))
    except OSError as exc:  # Guard against race condition
        if exc.errno != errno.EEXIST:
            raise


def chop(value, ending):
    if value.endswith(ending):
        return value[:-len(ending)]
    return value


def generate_template(template, output_folder):
    template_content = template.render(os.environ)
    target_file = os.path.join(output_folder, template.name)
    target_file = chop(target_file, '.template')
    create_directory(target_file)
    with open(target_file, 'w') as writer:
        writer.write(template_content)


def main(args=None):
    if args is None:
        args = sys.argv[1:]

    parser, args = parse_option(args)

    file_system_loader = FileSystemLoader(args.input_folder)
    env = Environment(
        loader=file_system_loader,
        undefined=StrictUndefined  # Fails if it tries to render undefined values
    )

    templates = [env.get_template(template_path) for template_path in env.list_templates()
                 if template_path.endswith(TEMPLATE) or TEMPLATE not in template_path]

    for template in templates:
        generate_template(template, args.output_folder)


if __name__ == "__main__":
    main()