Python cryptograpy.fernet doesn't decrypt symbols properly as expected - python-3.x

Question

Folks, I'm writing a simple cli tool to encrypt a text and decrypt based on the passed arguments.
It works fine when I use only text. But It behaves strange when I pass some symbols.
MY SOURCE CODE
import argparse
from cryptography.fernet import Fernet
def generate_key():
"""
Generates a key and save it into a file
"""
key = Fernet.generate_key()
with open("secret.key", "wb") as key_file:
key_file.write(key)
return key
def load_key():
"""
Loads the key named 'secret.key' from current directory
"""
return open("secret.key", "rb").read()
def encrypt_message(message):
"""
Encrypts a message
"""
key = load_key()
encoded_msg = message.encode()
f = Fernet(key)
encrypted_message = f.encrypt(encoded_msg)
with open("encrypted.txt", "wb") as encrypted_file:
encrypted_file.write(encrypted_message)
return encrypted_message
def decrypt_message(encrypted_msg):
"""
Decrypt an encrypted message
"""
key = load_key()
f = Fernet(key)
decrypted_message = f.decrypt(encrypted_msg)
return decrypted_message.decode()
def Main():
parser = argparse.ArgumentParser()
parser.add_argument("-e", "--en_crypt", help="Pass the text to encrypt as an argument")
parser.add_argument("-d", "--de_crypt", help="Pass the text to decrypt as an argument", action="store_true")
parser.add_argument("-k", "--key", help="Generate the 'secret.key' file", action="store_true")
args = parser.parse_args()
if args.en_crypt:
enc = encrypt_message(args.en_crypt)
print(enc)
if args.de_crypt:
with open("encrypted.txt", "rb") as file:
txt = file.read()
print(decrypt_message(txt))
if args.key:
result = generate_key()
print("Key Generated -> " + str(result))
if __name__ == "__main__":
Main()
MY TEST-CASE 1 - (This is successfully decrypting the text passed)
$ python3 01_crypt.py -k
Key Generated -> b'N5Ll6414I8nvcMlBytk8VwdFC4oVZZZMTCVTLpQ9big='
$ python3 01_crypt.py -e "Some Sample Text to Encrypt"
b'gAAAAABfVMU3JxZOrwLIudKLAqzq5IhivhhkyvJ6TMDxM-MmVQywo4AiZ1zGK5F5gO5JFXfHznV5zPjz6sD8qhOpIR_60Hq4_YLVIV0ztPAWBjln6reg1S0='
$ python3 01_crypt.py -d
Some Sample Text to Encrypt
MY TEST-CASE 2 - (This is not working as expected)
$ python3 01_crypt.py -k
Key Generated -> b'UDUpsIP-Ltjz8XGm-BUSwApXYE_L8eFl6rmE1yBbYW4='
$ python3 01_crypt.py -e "P#$$w0rD"
b'gAAAAABfVMX4tSIU4T1CM5Sw9jGR_O2cuIhccEM4htVTkerQD0YxWuCoUZeDWOeMIfpcP4HV7vYKmrxD22sf7yk27hGCdx0jQA=='
$ python3 01_crypt.py -d
P#4103w0rD
As per the test-case 2, My expected output should be same as the encrypted one P#$$w0rD but instead it shows as P#4103w0rD
I'm clueless why this happen. Am I missing something important? Please advice.
Thanks in Advance!
ADDITIONAL NOTE
When I try the same facility without argparse It works as expected. Please review the code below,
from cryptography.fernet import Fernet
def key_generate():
"""
Generates a key and save it into a file
"""
key = Fernet.generate_key()
with open("secret.key", "wb") as key_file:
key_file.write(key)
return key
def load_keys():
"""
Loads the generated key named 'secret.key' from current directory
"""
return open("secret.key", "rb").read()
def encrypt_message(message):
"""
Encrypts a message
"""
key = load_keys()
encoded_msg = message.encode()
f = Fernet(key)
encrypted_message = f.encrypt(encoded_msg)
return encrypted_message
def decrypt_message(encrypted_msg):
"""
Decrypt an encrypted message
"""
key = load_keys()
f = Fernet(key)
decrypted_message = f.decrypt(encrypted_msg)
# print(type(encrypted_msg))
return decrypted_message.decode()
if __name__ == "__main__":
key_generate()
load_keys()
PLAINTEXT = "P#$$w0rD"
print("Plain Text", PLAINTEXT)
ENCRYPTED_TEXT = encrypt_message(PLAINTEXT)
print("Encrypted Text", ENCRYPTED_TEXT)
DECRYPTED_TEXT = decrypt_message(ENCRYPTED_TEXT)
print("Decrypted Text", DECRYPTED_TEXT)
OUTPUT
$python3 02_decrypt.py
Plain Text P#$$w0rD
Encrypted Text b'gAAAAABfVMfzv7H--aTCaUBdHVs05VRbFmuqpnrt-7k1NCTY9FrGMZKH8y2pkKqZsu5oxRqRgp5DzyRHZhfmA9p_cgNniWfsNw=='
Decrypted Text P#$$w0rD
The above behaviour makes me suspect, argparse could be culprit. Please advice.

Answer 1

Argparse is not at fault, your usage of your shell is.
python3 01_crypt.py -e "P#$$w0rD"
has your Unix shell substitute the current PID for $$ (which happened to be 4103).
Use single quotes to avoid the substitution.
python3 01_crypt.py -e 'P#$$w0rD'