C.c in Python using single comments file (barely tested)

c.py

#!/usr/bin/env python

# works with python2.6+

import argparse
import json
import os

_COMMENT_FILE = os.path.expanduser('~/.comments')


class Comments(object):
    def __init__(self, comments_file):
        self.comments_file = comments_file

    def __enter__(self):
        try:
            with open(self.comments_file, 'r') as cf:
                self.comments = json.load(cf)
        except:
            self.comments = {}

        return self.comments

    def __exit__(self, exc_type, exc_val, exc_tb):
        with open(self.comments_file, 'w') as cf:
            json.dump(self.comments, cf)


if __name__ == '__main__':

    parser = argparse.ArgumentParser(description='Commenter')

    parser.add_argument('target', help='file or directory')
    parser.add_argument('comment', nargs='?', help='file or directory')
    parser.add_argument('-a', '--all', action='store_true',
                        help='show all comments at or below target directory')

    args = parser.parse_args()
    path = os.path.abspath(args.target)

    with Comments(_COMMENT_FILE) as comments:
        if args.comment:
            comments[path] = args.comment
        else:
            if args.all and os.path.isdir(path):
                for p in sorted(comments):
                    if p.startswith(path):
                        print p, comments[p]
            else:
                try:
                    print comments[path]
                except KeyError:
                    pass