Convert Minecraft language file from properties to JSON format

lang2json.py

import sys
import codecs

usage = '''
Usage: python lang2json.py some.lang
Python 3 please
'''


def convert(file):
    assert file.endswith(".lang")
    output = "{\n"
    with codecs.open(file, 'r', 'utf-8') as f:
        for line in f:
            if not line.startswith('#') and '=' in line:
                words = line[:-1].split('=')
                output += '  ' + '"{:s}": "{:s}",\n'.format(words[0], words[1].replace('"', '\\"'))
    output += '}\n'
    with codecs.open(file[:-5] + '.json', 'w', 'utf-8') as f:
        f.write(output)


if __name__ == '__main__':
    if len(sys.argv) == 1:
        print(usage)
    elif len(sys.argv) == 2:
        convert(sys.argv[1])