Update using passed parameters instead of global variables.

Caeser-Cipher/caeser-cipher.py

@@ -1,4 +1,4 @@
-# Python Caeser Cipher Helper v1.0.2
+# Python Caeser Cipher Helper v1.1.0
 # Usage (encrypt): python3 caeser-cipher.py encrypt secretmessage
 # Usage (decrypt): python3 caeser-cipher.py decrypt secretmessage
 
@@ -19,19 +19,14 @@ shiftNum = input("Please enter the shift you would like to use (Just hit enter i
 ciphertext = re.sub (r'([^a-zA-Z]+?)', '', ciphertext) # Remove all non-letters.
 ciphertext = ciphertext.lower() # Make it all lowercase. https://www.geeksforgeeks.org/isupper-islower-lower-upper-python-applications/
 letters = list(string.ascii_lowercase) # Use a list of lowercase letters. https://stackoverflow.com/questions/43918437/how-to-iterate-through-the-alphabet
-letterCount = 0 # Set variable for keeping track of which letter in the ciphertext we're on.
-letterPos = 0 # Set variable for keeping track of the letter's position in the alphabet.
-answer = "" # The solution.
-commonletter = 0
 
-def encrypt():
-    # Grab global variables.
-    global ciphertext
-    global shiftNum
-    global letters
-    global letterCount
-    global letterPos
-    global answer
+def encrypt(ciphertext, shiftNum, letters): # Grab parameters
+
+    # Create local variables for this function.
+
+    letterCount = 0
+    letterPos = 0
+    answer = ""
 
     for c in ciphertext: # For every letter in the ciphertext
         while letterPos < 26: # While the letter's position in the alphabet is less than 26 (and thus valid), continue.
@@ -56,16 +51,13 @@ def encrypt():
     print("\nYour enciphered text is: " + answer)
 
 
-def decrypt():
+def decrypt(ciphertext, shiftNum, letters, commonletter): # Grab parameters
 
-    # Grab global variables.
-    global ciphertext
-    global shiftNum
-    global letters
-    global letterCount
-    global letterPos
-    global answer
-    global commonletter
+    # Create local variables for this function.
+
+    letterCount = 0
+    letterPos = 0
+    answer = ""
 
     for c in ciphertext: # For every letter in the ciphertext
         while letterPos < 26: # While the letter's position in the alphabet is less than 26 (and thus valid), continue.
@@ -90,13 +82,13 @@ def decrypt():
     print("\nYour decrypted text is: " + answer)
 
 
-def freq():
-    # Grab global variables.
-    global ciphertext
-    global commonletter
-    global letterPos
-    global shiftNum
-    print(shiftNum)
+def freq(ciphertext):
+    # Create local variables for this function.
+
+    commonletter = 0
+    letterCount = 0
+    letterPos = 0
+    answer = ""
 
     commonletter = collections.Counter(ciphertext).most_common()[0][0] # Find most common letter and thus the shift https://stackoverflow.com/questions/47251934/how-to-count-the-most-frequent-letter-in-a-string
 
@@ -113,13 +105,13 @@ def freq():
 
             letterPos = letterPos + 1 # Iterate through letter positions in the alphabet. (neccessary to find one that matches.)
 
-    decrypt() # Decrypt using the frequency found in here.
+    decrypt(ciphertext, shiftNum, letters, commonletter) # Decrypt using the frequency found in here.
 
 
 if action == "encrypt":
-    encrypt()
+    encrypt(ciphertext, shiftNum, letters) # Start the encrypt() function while passing 3 variables as parameters.
 if action == "decrypt":
     if shiftNum == "":
-        freq()
+        freq(ciphertext)
     else:
-        decrypt()
+        decrypt(ciphertext, shiftNum, letters, commonletter)

passing-parms.py

@@ -0,0 +1,9 @@
+def no_side_effects(cities, cows):
+    print(cities)
+    cities = cities + ["Birmingham", "Bradford"]
+    print(cities)
+    print(cows)
+
+locations = ["London", "Leeds", "Glasgow", "Sheffield"]
+
+no_side_effects(locations, "Fred")