Pendulum Code

def pendulum(string):
    result = ""
    side = 0
    while len(string)>0:
        if side == 0:
            result = string[0] + result
        else:
            result = result + string[0]
        string = string[1:]
        side = 1 - side
    return result
def antipendulum(string):
    result = ""

    index = (len(string)-1) // 2
    swing = 1
    swing_dir = 1

    while index>=0 and index<len(string):
        result += string[index]
        index += swing * swing_dir
        swing += 1
        swing_dir = -swing_dir

    return result

def encrypt():
    while True:
        pt = input("Plaintext: ")

        if pt == "": break
        ct = pendulum(pt)

        print("Ciphertext: \""+ct+"\"")
def decrypt():
    while True:
        ct = input("Ciphertext: ")

        if ct == "": break
        pt = antipendulum(ct)

        print("Plaintext: \""+pt+"\"")
encrypt()
##decrypt()