create monoalphabetic cipher

ciphers/mono_alphabetic_ciphers.py

@@ -0,0 +1,65 @@
+LETTERS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+
+
+def translate_message(key, message, mode):
+    """
+    >>> translate_message("QWERTYUIOPASDFGHJKLZXCVBNM", "When you do the common things in life in an uncommon way, you will command the attention of the world", "encrypt")
+    'Vitf ngx rg zit egddgf zioful of soyt of qf xfegddgf vqn, ngx voss egddqfr zit qzztfzogf gy zit vgksr'
+    """
+    translated = ""
+    charsA = LETTERS
+    charsB = key
+    if mode == "decrypt":
+        # For decrypting, we can use the same code as encrypting. We
+        # just need to swap where the key and LETTERS strings are used.
+        charsA, charsB = charsB, charsA
+    # loop through each symbol in the message
+    for symbol in message:
+        if symbol.upper() in charsA:
+            # encrypt/decrypt the symbol
+            symIndex = charsA.find(symbol.upper())
+            if symbol.isupper():
+                translated += charsB[symIndex].upper()
+            else:
+                translated += charsB[symIndex].lower()
+        else:
+            # symbol is not in LETTERS, just add it
+            translated += symbol
+    return translated
+
+
+def encrypt_message(key: str, message: str) -> str:
+    """
+    >>> encrypt_message("QWERTYUIOPASDFGHJKLZXCVBNM", "When you do the common things in life in an uncommon way, you will command the attention of the world")
+    'Vitf ngx rg zit egddgf zioful of soyt of qf xfegddgf vqn, ngx voss egddqfr zit qzztfzogf gy zit vgksr'
+    """
+    return translate_message(key, message, "encrypt")
+
+
+def decrypt_message(key, message):
+    """
+    >>> decrypt_message("QWERTYUIOPASDFGHJKLZXCVBNM", "When you do the common things in life in an uncommon way, you will command the attention of the world")
+    'Bpcy fig mi epc vizziy ephyol hy shnc hy ky gyvizziy bkf, fig bhss vizzkym epc keecyehiy in epc bidsm'
+    """
+    return translate_message(key, message, "decrypt")
+
+
+def main():
+    myMessage = "When you do the common things in life in an uncommon way, you will command the attention of the world"
+    myKey = "QWERTYUIOPASDFGHJKLZXCVBNM"
+    myMode = "decrypt"  # set to 'encrypt' or 'decrypt'
+
+    if myMode == "encrypt":
+        translated = encrypt_message(myKey, myMessage)
+    elif myMode == "decrypt":
+        translated = decrypt_message(myKey, myMessage)
+    print("Using key %s" % (myKey))
+    print("The %sed message is:" % (myMode))
+    print(translated)
+
+
+if __name__ == "__main__":
+    import doctest
+
+    doctest.testmod()
+    main()