Convert between pickle and json sequences

picklejson.py

import sys
import pickle
import json

def usage():
    print("Usage:")
    print(f"\t{sys.argv[0]} --tojson [PICKLE FILES]")
    print(f"\t{sys.argv[0]} --topickle [JSON FILES]")

JD = json.JSONDecoder()

def pickle_to_json(pklf, jsonf):
    try:
        while True:
            json.dump(pickle.load(pklf), jsonf)
    except EOFError:
        return

def json_to_pickle(jsonf, pklf):
    jdata = jsonf.read().strip()
    idx = 0
    while idx < len(jdata):
        obj, s = JD.raw_decode(jdata[idx:])
        pickle.dump(obj, pklf)
        idx += s

def pickle_to_json_all(filenames):
    for filename in filenames:
        if filename.endswith('.pkl'):
            outname = filename[:-4] + '.json'
        else:
            outname = filename
        with open(filename, 'rb') as pklf, open(outname, 'w') as jsonf:
            pickle_to_json(pklf, jsonf)

def json_to_pickle_all(filenames):
    for filename in filenames:
        if filename.endswith('.json'):
            outname = filename[:-5] + '.pkl'
        else:
            outname = filename
        with open(filename) as jsonf, open(outname, 'wb') as pklf:
            json_to_pickle(jsonf, pklf)

if __name__ == '__main__':
    if len(sys.argv) == 1:
        usage()
    elif sys.argv[1] == '--tojson':
        pickle_to_json_all(sys.argv[2:])
    elif sys.argv[1] == '--topickle':
        json_to_pickle_all(sys.argv[2:])
    else:
        usage()