python3 pySerial TypeError: unicode strings are not supported, please encode to bytes:

Question

In Python 3 I imported the pySerial library so I could communicate with my Arduino Uno by serial commands.
It worked very well in Python 2.7 but in Python 3 I keep running into a error it says this

TypeError: unicode strings are not supported, please encode to bytes: 'allon'

In Python 2.7 the only thing I did differently is use raw_input but I don't know what is happening in Python 3. Here is my code

    import serial, time
    import tkinter
    import os








    def serialcmdw():
    os.system('clear')
    serialcmd = input("serial command: ")
    ser.write (serialcmd)
    serialcmdw()

    ser = serial.Serial()
    os.system('clear')
    ser.port = "/dev/cu.usbmodem4321"
    ser.baudrate = 9600
    ser.open()
    time.sleep(1)
    serialcmdw()

Answer 1

Encode your data which you are writing to serial,in your case "serialcmd" to bytes.try the following :

ser.write(serialcmd.encode())

Answer 2

i found same you problem for learn "Arduino Python Serial"
You can do another way this:

ser.write(str.encode('allon'))