encode/decode data in file

#!/usr/bin/python3

import os
import struct
from Crypto.Cipher import AES
import hashlib
import getpass


def encryption_file(in_filename, key, chunksize=64*1024):

    out_filename = in_filename + '.enc'

    TheHash = hashlib.sha256(key.encode('utf-8')).hexdigest()
    key = TheHash[0:32]

    IV = b'rp1\\\xe6@\x04\x13\x7f\x81\x1d<\x0b\x13\x1a@'
    encryptor = AES.new(key, AES.MODE_CBC, IV)
    file_size = os.path.getsize(in_filename)

    with open(in_filename, 'rb') as infile:
        with open(out_filename, 'wb') as outfile:
            outfile.write(struct.pack('<Q', file_size))
            outfile.write(IV)

            while True:
                chunk = infile.read(chunksize)

                if len(chunk) == 0:
                    break
                elif len(chunk) % 16 != 0:
                    chunk += ' '.encode('utf-8') * (16 - len(chunk) % 16)

                text = encryptor.encrypt(chunk)
                print('[DEBUG]: encrypted:', text)
                outfile.write(text)

        os.unlink(in_filename)


def decrypt_file(in_filename, key, chunksize=64*1024):

    out_filename = os.path.splitext(filename)[0]

    TheHash2 = hashlib.sha256(key.encode('utf-8')).hexdigest()
    key = TheHash2[0:32]

    #IV = b'rp1\\\xe6@\x04\x13\x7f\x81\x1d<\x0b\x13\x1a@'
    #print(len(IV))

    with open(filename, 'rb') as infile:
        file_size = struct.unpack('<Q', infile.read(struct.calcsize('Q')))[0]
        IV = infile.read(16) # len(IV)
        decryptor = AES.new(key, AES.MODE_CBC, IV)

        with open(out_filename, 'wb') as outfile:
            while True:
                chunk = infile.read(chunksize)

                if len(chunk) == 0:
                    break

                text = decryptor.decrypt(chunk)
                print('[DEBUG]: decrypted:', text)
                outfile.write(text)

            outfile.truncate(file_size)
        os.unlink(in_filename)

#----------------------------------------------------------

choice = input("(E)ncrypt or (D)ecrypt: ").lower()

if choice == 'e':
    #filename = input("Enter filename: ")
    #key = getpass.getpass("Enter password: ")
    filename = 'test.txt'
    key = 'hello world'
    encryption_file(filename, key)
elif choice == 'd':
    #filename = input("Enter filename: ")
    #key = getpass.getpass("Enter password: ")
    filename = 'test.txt.enc'
    key = 'hello world'
    decrypt_file(filename, key)
else:
    print("Select E or D")