c2j -- dsl for generating json

c2j.py

#!/usr/bin/env python3

import json
import sys


class c2j:
    def __init__(self):
        self.stack = []
        self.root = None
        self.current_key = None

    @property
    def top(self):
        return self.stack[-1]

    def contain(self, obj):
        if not self.stack:
            return
        if isinstance(self.top, dict):
            if not self.current_key:
                raise ValueError("no current key")
            self.top[self.current_key] = obj
            self.current_key = None
        elif isinstance(self.top, list):
            self.top.append(obj)
        else:
            raise TypeError("invalid value on stack")

    def append(self, obj):
        if not self.stack:
            self.root = obj
        self.stack.append(obj)

    def process_line(self, line):
        line = line.rstrip("\r\n").split(None, 1)
        verb = line.pop(0).lower()
        if verb == "obj":
            obj = {}
            self.contain(obj)
            self.append(obj)
        elif verb == "array":
            obj = []
            self.contain(obj)
            self.append(obj)
        elif verb == "key":
            if not isinstance(self.top, dict):
                raise ValueError("can not use key when no obj on top of stack")
            self.current_key = line[0]
        elif verb == "string":
            self.contain(line[0])
        elif verb == "number":
            self.contain(float(line[0]) if "." in line[0] else int(line[0]))
        elif verb == "true":
            self.contain(True)
        elif verb == "false":
            self.contain(False)
        elif verb == "null":
            self.contain(None)
        elif verb == "end":
            self.stack.pop(-1)
        else:
            raise ValueError("unknown verb " + verb)


if __name__ == "__main__":
    c = c2j()

    for line in sys.stdin:
        c.process_line(line)

    print(json.dumps(c.root, indent=2, sort_keys=True))

test.sh

#!/bin/bash

(
	echo obj
	for x in a b c d; do
		echo key $x
		echo array
		echo number $RANDOM
		echo number $RANDOM
		echo number $RANDOM
		echo end
	done
) | python3 c2j.py