render-template.py

#!/usr/bin/env python3
import argparse
import json
import pystache
import sys

ap = argparse.ArgumentParser()
ap.add_argument("--template", metavar="FILE", help="Mustache template file")
ap.add_argument("--data", metavar="FILE", help="JSON data file")
ap.add_argument("--schema", metavar="FILE", help="JSON schema file")
ap.add_argument("--output", metavar="FILE", help="Generated output file")
args = ap.parse_args()

if args.data:
    with open(args.data, "r") as fh:
        context = json.load(fh)
else:
    raise ValueError("data file not specified")

if args.schema:
    import jsonschema
    with open(args.schema, "r") as fh:
        schema = json.load(fh)
    jsonschema.validate(context, schema)

if args.template:
    with open(args.template, "r") as fh:
        template = fh.read()
else:
    template = sys.stdin.read()

output = pystache.render(template, context)

if args.output:
    with open(args.output, "w") as fh:
        fh.write(output)
else:
    sys.stdout.write(output)