Includes basic Caesar cipher encode/decode and an assisted brute force decode. (Python 3.3.2)

Caesar Cipher.py

def init_(): # Initializes the program
  startup = input("Encode or decode with key or decode without key? (ed/dwok)\n> ").lower()
  if startup == "dwok": # "dwok" means decode without key.
    caesar_cipher_hiddenkey_decode()
  elif startup == "ed": # "ed" means encode/decode.
    caesar_cipher()
  else:
    print("It looks like you didn't input ed or dwok. Try again please.")
    startup_()

def isInt_(x):
  try:
    int(x)
    return True
  except ValueError:
    return False

def caesar_cipher(): # Encodes or decodes with a key
  text = input("\nInput your message.\n> ")
  key = int(input("\nInput your integer key.\n> "))
  mode = input("\nEncode or decode?\n> ")
  alphabet = "abcdefghijlmnopqrstuvwxyz"
  newText = "" # text = list(text) is unnecessary here
  if mode == "decode": # Reverses the direction of the inputted shift
    key = -key
    print("\nDecoding...\n")
  else:
    print("\nEncoding...\n")
  '''
  The following loop iterates through the index values up to the length of the inputted text. 
  For each index value plus the shift value of the letter in the inputted text, 
  the loop stores the corresponding letter in newLetter. 
  The modulus is to correct for values outside of the alphabet range. 
  Finally, the newLetter is added to the newText string.
  Along the way, some corrections are made for special cases.
  Really, it's easiest to tell what's going on using the PythonTutor.com Visualizer.
  '''
  for char in range(len(text)):
    if text[char].isupper():
      alphabet = alphabet.upper()
    elif text[char].islower():
      alphabet = alphabet.lower()
    if text[char].isalpha() == False: # Exception for non-letters
      if isInt_(text[char]):
        newLetter = str((int(text[char]) + key)%10)
      else:
        newLetter = text[char]
    else:
      newLetter = alphabet[((alphabet.index(text[char])+key)%25)]
    newText += newLetter
  print("Result:", newText)

def caesar_cipher_hiddenkey_decode(): # Decodes one step at a time with user input
  text = input("\nInput your message to decode.\n> ")
  alphabet = "abcdefghijlmnopqrstuvwxyz"
  key = 1
  not_done = ""
  while not_done == "":
    newText = ""
    print("\nDecoding...\n")
    for char in range(len(text)):
      if text[char].isupper():
        alphabet = alphabet.upper()
      elif text[char].islower():
        alphabet = alphabet.lower()
      if text[char].isalpha() == False:
        if isInt_(text[char]):
          newLetter = str((int(text[char]) - key)%10)
        else:
          newLetter = text[char]
      else:
        newLetter = alphabet[((alphabet.index(text[char])-key)%25)]
      newText += newLetter
    key += 1 # Iterate through all possible key values one step at a time.
    print("Result: " + newText)
    not_done = input("\nInput something if done.\n> ") # User can tell the script when to stop cycling.
  print("\nDone!\n\nThe final result is: " + newText)



init_() # Begins the script

is there any error here I put:
message: hello there
key: 5675
encode
result: hello there

any error? I missing?