Encrypt/Decrypt RC4 by a String Key

rc4.py

import sys

def rc4init(key):
  x=0
  box = range(256)
  for i in range(256):
    x = (x + box[i] + ord(key[i % len(key)])) % 256
    box[i], box[x] = box[x], box[i]
  return box

def rc4crypt(data, box):
  x=0
  y=0
  out = []
  for char in data:
    x = (x + 1) % 256
    y = (y + box[x]) % 256
    box[x], box[y] = box[y], box[x]
    out.append(chr(ord(char) ^ box[(box[x] + box[y]) % 256]))
  return ''.join(out)

argvs = sys.argv
argc = len(argvs)

if (argc !=4):
  print "python ./rc4.py file1 file2 key"
  quit()

with open(argvs[1], mode='rb') as file:
  fileContent = file.read()

sbox=rc4init(argvs[3])
decdata=rc4crypt(fileContent, sbox)
with open(argvs[2], 'wb') as EncOrDecrypted_file:
    EncOrDecrypted_file.write(decdata)