Dead simple command line NBT editor

mc-nbt.py

#!/usr/bin/env python
# Name: mc-nbt
# Version: 0.1
# Description: Views or edits a Minecraft NBT file
# Author: Ethan Reesor <firelizzard@gmail.com>
# License: DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE <http://www.wtfpl.net/>

# Examples:
#   Print entire file:
#     mc-nbt FILE
#   Print part of the tree:
#     mc-nbt FILE --path Pos
#   Set a tag's value (element of a list):
#     mc-nbt FILE --path Pos.0 1024.0
#   Set a list tag's elements' values to elements of a list:
#     mc-nbt FILE --path Pos [1,2,3]

from nbt import nbt
import argparse

def main():
    parser = argparse.ArgumentParser(description='Manage an NBT file')
    parser.add_argument(dest='file', type=lambda x: nbt.NBTFile(x, 'rb'))
    parser.add_argument('--path', type=lambda x: x.split('.'), default=[])
    parser.add_argument('--value', type=eval)

    args = parser.parse_args()

    last = None
    item = args.file
    if args.path:
        for name in args.path:
            last = item
            if type(item) is nbt.TAG_List:
                item = item[int(name)]
            else:
                item = item[name]

    if args.value is None:
        print(item.pretty_tree())
    elif not last:
        raise ValueException('Cannot specify --value without --path')
    elif type(item) is nbt.TAG_List and type(args.value) is list:
        for elem, value in zip(item, args.value):
            elem.value = value
        args.file.write_file()
    else:
        item.value = args.value
        args.file.write_file()

main()