Mobile CSP Cipher App

cipher.py

import math
def main():
    optionsList = ["Encrypt a message", "Encrypt a message with modified spacing", "Decrypt a message", "Decrypt a message and remove spacing", "Quit"]
    correctInput = False
    userChoice = 0
    userString = ""
    userOffset = 0
    newMessage = ""

    print("====Welcome to [CipherApp]====")
    
    #prints options and gets user's choice until user enters correctly
    while (correctInput != True):
        print("\nOptions:")
        for i in range(len(optionsList)):
            print("[" + str(i+1) + "]", optionsList[i])
        
        userChoice = eval(input("Enter the number for one of the above options: "))
        if (userChoice < 1 or userChoice > len(optionsList)):
            print("Invalid input: please enter the number for one of the options above.")
        else:
            correctInput = True
    
    #EXITS THE PROGRAM (caps to make it stand out for debugging purposes)
    if (userChoice == 5):
        exit()

    userString = input("Enter the message: ")
    #ensures that the offset will always be a positive whole number.
    userOffset = int(math.fabs(eval(input("Enter the cipher offset: "))))


    #why doesn't python have switch statements :(
    if (userChoice == 1):
        newMessage = encrypt(userString, userOffset, False)
    elif (userChoice == 2):
        newMessage = encrypt(userString, userOffset, True)
    elif (userChoice == 3):
        newMessage = decrypt(userString, userOffset, False)
    elif (userChoice == 4):
        newMessage = decrypt(userString, userOffset, True)
    
    print ("The new message is:", newMessage)

#encrypts the message with a caesar cipher with optional custom space formatting
def encrypt(message, offset, useCustomFormatting):
    plainSymbols = ["abcdefghijklmnopqrstuvwxyz", "ABCDEFGHIJKLMNOPQRSTUVWXYZ", "0123456789", "`~!@#$%^&*()_+-={}[]:;\"\'<>,.?/|\\", " "]
    cipherSymbols = []

    encMessage = ""

    #generates the cipher symbol sets based on the offset provided
    for i in range(len(plainSymbols)):
        cipherSymbols.append("")
        for j in range(len(plainSymbols[i])):
            cipherSymbols[i] += plainSymbols[i][(j + offset) % len(plainSymbols[i])]

    #If useCustomFormatting is true, removes spaces so they can be reform
    if (useCustomFormatting):
        message = "".join(message.split())


    for i in range(len(message)):
        foundSymbol = False
        for j in range(len(cipherSymbols)):
            if (foundSymbol == False and plainSymbols[j].find(message[i]) != -1):
                
                #for the sake of readability I separated this into two lines
                index = plainSymbols[j].find(message[i])
                encMessage += cipherSymbols[j][index]
                
                #since any character will only fall into one group, then the loop will terminated after one is successfully found
                break

        if (useCustomFormatting and (i + 1) % 4 == 0):
            encMessage += ' '

    return encMessage

#decrypts a caesar cipher message with optional removal of spaces
def decrypt(message, offset, useCustomFormatting):
    decMessage = ""
    decMessage = encrypt(message, -offset, False)
    
    if (useCustomFormatting):
        decMessage = "".join(decMessage.split())

    return decMessage
main()