Encryption and Decryption of text/files using pycrypto

pycrypt.py

#!/usr/bin/python3

import sys
from Crypto import Random
from Crypto.Cipher import AES
import argparse

class Initialize:

    def argsparser(self):
        '''
        To use arguments from command line.
        '''
        
        parser = argparse.ArgumentParser(description='')
        parser.add_argument('--input', dest='input', default='yolov3.weights', help='Input video source', type=str)
        parser.add_argument('--encrypt', dest='encrypt', default=False, help='To Encrypt', action='store_true')
        parser.add_argument('--decrypt', dest='decrypt', default=False, help='To Decrypt', action='store_true')
        return parser.parse_args()

    def __init__(self):
        self.args = self.argsparser()
        if(self.args.encrypt and self.args.decrypt) or (not self.args.encrypt and not self.args.decrypt):
            print('Please Select a valid input')
            sys.exit()

class Security:

    def pad(self, s):
        return s + b"\0" * (AES.block_size - len(s) % AES.block_size)

    def encrypt(self, message):
        message = self.pad(message)
        iv = Random.new().read(AES.block_size)
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        return iv + cipher.encrypt(message)

    def decrypt(self, ciphertext):
        iv = ciphertext[:AES.block_size]
        cipher = AES.new(self.key, AES.MODE_CBC, iv)
        plaintext = cipher.decrypt(ciphertext[AES.block_size:])
        return plaintext.rstrip(b"\0")

    def encrypt_file(self, file_name):
        with open(file_name, 'rb') as fo:
            plaintext = fo.read()
        enc = self.encrypt(plaintext)
        with open(file_name + ".enc", 'wb') as fo:
            fo.write(enc)

    def decrypt_file(self, file_name):
        with open(file_name, 'rb') as fo:
            ciphertext = fo.read()
        dec = self.decrypt(ciphertext)
        with open(file_name[:-4], 'wb') as fo:
            fo.write(dec)

    def __init__(self):
        self.key = 'Add a key here'
        self.key_size = 256

if __name__ == '__main__':
    init = Initialize()
    sec = Security()
    if(init.args.encrypt):
        sec.encrypt_file(init.args.input)
    
    if(init.args.decrypt):
        sec.decrypt_file(init.args.input)