Pyupgrade to Python 3.9 (#4718)

* Pyupgrade to Python 3.9

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

ciphers/caesar_cipher.py

@@ -1,8 +1,9 @@
+from __future__ import annotations
+
 from string import ascii_letters
-from typing import Dict, Optional
 
 
-def encrypt(input_string: str, key: int, alphabet: Optional[str] = None) -> str:
+def encrypt(input_string: str, key: int, alphabet: str | None = None) -> str:
     """
     encrypt
     =======
@@ -80,7 +81,7 @@ def encrypt(input_string: str, key: int, alphabet: Optional[str] = None) -> str:
     return result
 
 
-def decrypt(input_string: str, key: int, alphabet: Optional[str] = None) -> str:
+def decrypt(input_string: str, key: int, alphabet: str | None = None) -> str:
     """
     decrypt
     =======
@@ -145,7 +146,7 @@ def decrypt(input_string: str, key: int, alphabet: Optional[str] = None) -> str:
     return encrypt(input_string, key, alphabet)
 
 
-def brute_force(input_string: str, alphabet: Optional[str] = None) -> Dict[int, str]:
+def brute_force(input_string: str, alphabet: str | None = None) -> dict[int, str]:
     """
     brute_force
     ===========

ciphers/decrypt_caesar_with_chi_squared.py

@@ -1,12 +1,11 @@
 #!/usr/bin/env python3
-
-from typing import Optional
+from __future__ import annotations
 
 
 def decrypt_caesar_with_chi_squared(
     ciphertext: str,
-    cipher_alphabet: Optional[list[str]] = None,
-    frequencies_dict: Optional[dict[str, float]] = None,
+    cipher_alphabet: list[str] | None = None,
+    frequencies_dict: dict[str, float] | None = None,
     case_sensetive: bool = False,
 ) -> tuple[int, float, str]:
     """

ciphers/diffie.py

@@ -1,7 +1,7 @@
-from typing import Optional
+from __future__ import annotations
 
 
-def find_primitive(n: int) -> Optional[int]:
+def find_primitive(n: int) -> int | None:
     for r in range(1, n):
         li = []
         for x in range(n - 1):

ciphers/shuffled_shift_cipher.py

@@ -1,6 +1,7 @@
+from __future__ import annotations
+
 import random
 import string
-from typing import Optional
 
 
 class ShuffledShiftCipher:
@@ -27,7 +28,7 @@ class ShuffledShiftCipher:
     cip2 = ShuffledShiftCipher()
     """
 
-    def __init__(self, passcode: Optional[str] = None) -> None:
+    def __init__(self, passcode: str | None = None) -> None:
         """
         Initializes a cipher object with a passcode as it's entity
         Note: No new passcode is generated if user provides a passcode