from Crypto.Cipher import AES
import json
import os

KEY_LENGTH = 256
BLOCK_LENGTH = 16

KEY_FILE = 'key'
ENCRYPTED_FILE = 'data'
DECRYPTED_FILE = 'tmp'

EOT_CHAR = '\x04'

def get_cipher(iv):
    try:
        key = open(KEY_FILE, 'rb').read()
    except IOError:
        key = input("Please enter the decryption key: ")
    return AES.new(key, AES.MODE_CBC, iv)

def encrypt():
    bytes = multiple_of(open(DECRYPTED_FILE, 'rt').read().encode(), BLOCK_LENGTH)
    iv = os.urandom(16)
    c = get_cipher(iv)
    return (iv, c.encrypt(bytes))

def decrypt():
    bytes = open(ENCRYPTED_FILE, 'rb').read()
    c = get_cipher(bytes[:16])
    return c.decrypt(bytes).decode('utf-8')

def multiple_of(bytes, length):
    if len(bytes) % length == 0:
        return bytes
    else:
        return bytes + (EOT_CHAR * (length - (len(bytes) % length))).encode()

from Crypto.Cipher import AES
import json
import os
import optparse

KEY_LENGTH = 256
BLOCK_LENGTH = 16

KEY_FILE = 'key'
ENCRYPTED_FILE = 'data'
DECRYPTED_FILE = 'tmp'

EOT_CHAR = '\x04'

def main(options, arguments):
    pass

def get_cipher(iv):
    try:
        key = open(KEY_FILE, 'rb').read()
    except IOError:
        key = input("Please enter the decryption key: ")
    return AES.new(key, AES.MODE_CBC, iv)

def encrypt():
    bytes = multiple_of(open(DECRYPTED_FILE, 'rt').read().encode(), BLOCK_LENGTH)
    iv = os.urandom(16)
    c = get_cipher(iv)
    return (iv, c.encrypt(bytes))

def decrypt():
    bytes = open(ENCRYPTED_FILE, 'rb').read()
    c = get_cipher(bytes[:16])
    return c.decrypt(bytes).decode('utf-8')

def multiple_of(bytes, length):
    if len(bytes) % length == 0:
        return bytes
    else:
        return bytes + (EOT_CHAR * (length - (len(bytes) % length))).encode()

if __name__ == '__main__':
    p = optparse.OptionParser()
    options, arguments = p.parse_args()
    main(options, arguments)

Add option parser and main method
Add option parser and main method

  from Crypto.Cipher import AES
  import json
  import os
+ import optparse
  
  KEY_LENGTH = 256
  BLOCK_LENGTH = 16
  
  KEY_FILE = 'key'
  ENCRYPTED_FILE = 'data'
  DECRYPTED_FILE = 'tmp'
  
  EOT_CHAR = '\x04'
+ 
+ def main(options, arguments):
+     pass
  
  def get_cipher(iv):
      try:
          key = open(KEY_FILE, 'rb').read()
      except IOError:
          key = input("Please enter the decryption key: ")
      return AES.new(key, AES.MODE_CBC, iv)
  
  def encrypt():
      bytes = multiple_of(open(DECRYPTED_FILE, 'rt').read().encode(), BLOCK_LENGTH)
      iv = os.urandom(16)
      c = get_cipher(iv)
      return (iv, c.encrypt(bytes))
  
  def decrypt():
      bytes = open(ENCRYPTED_FILE, 'rb').read()
      c = get_cipher(bytes[:16])
      return c.decrypt(bytes).decode('utf-8')
  
  def multiple_of(bytes, length):
      if len(bytes) % length == 0:
          return bytes
      else:
          return bytes + (EOT_CHAR * (length - (len(bytes) % length))).encode()
  
+ if __name__ == '__main__':
+     p = optparse.OptionParser()
+     options, arguments = p.parse_args()
+     main(options, arguments)
+ 
Add option parser and main method
## Code Before:
from Crypto.Cipher import AES
import json
import os

KEY_LENGTH = 256
BLOCK_LENGTH = 16

KEY_FILE = 'key'
ENCRYPTED_FILE = 'data'
DECRYPTED_FILE = 'tmp'

EOT_CHAR = '\x04'

def get_cipher(iv):
    try:
        key = open(KEY_FILE, 'rb').read()
    except IOError:
        key = input("Please enter the decryption key: ")
    return AES.new(key, AES.MODE_CBC, iv)

def encrypt():
    bytes = multiple_of(open(DECRYPTED_FILE, 'rt').read().encode(), BLOCK_LENGTH)
    iv = os.urandom(16)
    c = get_cipher(iv)
    return (iv, c.encrypt(bytes))

def decrypt():
    bytes = open(ENCRYPTED_FILE, 'rb').read()
    c = get_cipher(bytes[:16])
    return c.decrypt(bytes).decode('utf-8')

def multiple_of(bytes, length):
    if len(bytes) % length == 0:
        return bytes
    else:
        return bytes + (EOT_CHAR * (length - (len(bytes) % length))).encode()

## Instruction:
Add option parser and main method
## Code After:
from Crypto.Cipher import AES
import json
import os
import optparse

KEY_LENGTH = 256
BLOCK_LENGTH = 16

KEY_FILE = 'key'
ENCRYPTED_FILE = 'data'
DECRYPTED_FILE = 'tmp'

EOT_CHAR = '\x04'

def main(options, arguments):
    pass

def get_cipher(iv):
    try:
        key = open(KEY_FILE, 'rb').read()
    except IOError:
        key = input("Please enter the decryption key: ")
    return AES.new(key, AES.MODE_CBC, iv)

def encrypt():
    bytes = multiple_of(open(DECRYPTED_FILE, 'rt').read().encode(), BLOCK_LENGTH)
    iv = os.urandom(16)
    c = get_cipher(iv)
    return (iv, c.encrypt(bytes))

def decrypt():
    bytes = open(ENCRYPTED_FILE, 'rb').read()
    c = get_cipher(bytes[:16])
    return c.decrypt(bytes).decode('utf-8')

def multiple_of(bytes, length):
    if len(bytes) % length == 0:
        return bytes
    else:
        return bytes + (EOT_CHAR * (length - (len(bytes) % length))).encode()

if __name__ == '__main__':
    p = optparse.OptionParser()
    options, arguments = p.parse_args()
    main(options, arguments)
