Towers of Hanoi

from stack import Stack

print("\nLet's play Towers of Hanoi!!")

#Create the Stacks
stacks = []
left_stack = Stack("Left")
middle_stack = Stack("Middle")
right_stack = Stack("Right")
stacks += [left_stack, middle_stack, right_stack]

#Set up the Game
num_disks = int(input("\nHow many disks do you want to play with?\n"))

while num_disks < 3:
  num_disks = int(input("Enter a number greater than or equal to 3\n"))

for disk in range(num_disks, 0, -1):
  left_stack.push(disk)
#left_stack.print_items()

num_optimal_moves = (2 ** num_disks) - 1
print("\nThe fastest you can solve this game is in {0} moves".format(num_optimal_moves))
#Get User Input

def get_input():
#  choices = ["""letter""" for stack in stacks]

  choices = [stack.get_name()[0] for stack in stacks]

  while True:
    
    for i in range(len(stacks)):
      name = stacks[i].get_name()
      letter = choices[i]
      print("Enter {0} for {1}".format(letter, name))

    user_input = input("")

    if user_input in choices:
      for i in range(len(stacks)):
        return stacks
        
#Play the Game
num_user_moves = 0

while right_stack.get_size() != num_disks:

  print("\n\n\n...Current Stacks...")
  for stack in stacks:
    stack.print_items()

  while True:

    print("\nWhich stack do you want to move from\n")
    from_stack = get_input()
    print("\nWhich stack do you want to move to?\n")
    to_stack = get_input()

    if from_stack.get_size() == 0:
      print("\n\nInvalid Move. Try Again")
    elif to_stack.get_size() == 0 or from_stack.peek() < to_stack.peek():
      disk = from_stack.pop()
      to_stack.push(disk)
      num_user_moves += 1
      break
    else:
      print("\n\nInvalid Move. Try Again")

print("\n\nYou completed the game in {0} moves, and the optimal number of moves is {1}".format(num_user_moves, num_optimal_moves))

Traceback (most recent call last):
  File "script.py", line 59, in <module>
    if from_stack.get_size() == 0:
AttributeError: 'list' object has no attribute 'get_size'