Continuous data streaming Arduino to Python
import serial
from Tkinter import *
ser = serial.Serial('/dev/tty.usbmodem621')
ser.baudrate = 9600
while 1 == 1:
    reading = ser.readline()
    root = Tk()
    w = Label(root, text = reading)
    w.pack()
    root.mainloop()

import serial
from Tkinter import *
from time import sleep
ser = serial.Serial('/dev/tty.usbmodem621')
ser.baudrate = 9600

def update():
    while 1:
        reading.set(ser.readline())
        root.update()
        sleep(1)

root=Tk()
reading = StringVar()

w = Label(root, textvariable = reading)
w.pack()

root.after(1,update)
root.mainloop()