MAINT: Updated f-string method (#6230)

* MAINT: Used f-string method

Updated the code with f-string methods wherever required for a better and cleaner understanding of the code.

* Updated files with f-string method

* Update rsa_key_generator.py

* Update rsa_key_generator.py

* Update elgamal_key_generator.py

* Update lru_cache.py

I don't think this change is efficient but it might tackle the error as the error was due to using long character lines.

* Update lru_cache.py

* Update lru_cache.py

Co-authored-by: cyai <seriesscar@gmail.com>
Co-authored-by: Christian Clauss <cclauss@me.com>

ciphers/transposition_cipher_encrypt_decrypt_file.py

@@ -12,10 +12,10 @@ def main() -> None:
     mode = input("Encrypt/Decrypt [e/d]: ")
 
     if not os.path.exists(inputFile):
-        print("File %s does not exist. Quitting..." % inputFile)
+        print(f"File {inputFile} does not exist. Quitting...")
         sys.exit()
     if os.path.exists(outputFile):
-        print("Overwrite %s? [y/n]" % outputFile)
+        print(f"Overwrite {outputFile}? [y/n]")
         response = input("> ")
         if not response.lower().startswith("y"):
             sys.exit()