Step By Step

First, we need to import our dependencies.

from tkinter import *
import serial.tools.list_ports
import functools

Now, get a list of available COM ports and initialize an instance of the serial object.

ports = serial.tools.list_ports.comports()
serialObj = serial.Serial()

Next, we need to create a window for our GUI. We are going to make the background grey

root = Tk()
root.config(bg='grey')

Next, we need to create a function to initialize our serial port. The user will ultimately select from a list of ports presented on the GUI.

def initComPort(index):
    currentPort = str(ports[index])
    comPortVar = str(currentPort.split(' ')[0])
    print(comPortVar)
    serialObj.port = comPortVar
    serialObj.baudrate = 9600
    serialObj.open()

Now, let's create buttons that are tied to each of our available COM ports in our GUI window

for onePort in ports:
    comButton = Button(root, text=onePort, font=('Calibri', '13'), height=1, width=45, command = functools.partial(initComPort, index = ports.index(onePort)))
    comButton.grid(row=ports.index(onePort), column=0)

Now let's create a Tkinter Canvas where we will display data being received from our Arduino.

dataCanvas = Canvas(root, width=600, height=400, bg='white')
dataCanvas.grid(row=0, column=1, rowspan=100)

Now let's create a vertical scrollbar so if our data window extends beyond the length of our GUI window, we can scroll to the bottom to see new data.

vsb = Scrollbar(root, orient='vertical', command=dataCanvas.yview)
vsb.grid(row=0, column=2, rowspan=100, sticky='ns')

dataCanvas.config(yscrollcommand = vsb.set)

Let's now anchor our Canvas into the rest of the GUI Frame.

dataFrame = Frame(dataCanvas, bg="white")
dataCanvas.create_window((10,0),window=dataFrame,anchor='nw')

Now let's create a function that will allow us to cyclically check for new data from our Arduino

def checkSerialPort():
    if serialObj.isOpen() and serialObj.in_waiting:
        recentPacket = serialObj.readline()
        recentPacketString = recentPacket.decode('utf').rstrip('\n')
        Label(dataFrame, text=recentPacketString)

We can now create an infinite loop using 'while True' that will run our GUI window and check for new data in the background.

while True:
    root.update()
    checkSerialPort()
    dataCanvas.config(scrollregion=dataCanvas.bbox("all"))

Full Script

from tkinter import *
import serial.tools.list_ports
import functools

ports = serial.tools.list_ports.comports()
serialObj = serial.Serial()

root = Tk()
root.config(bg='grey')

def initComPort(index):
    currentPort = str(ports[index])
    comPortVar = str(currentPort.split(' ')[0])
    print(comPortVar)
    serialObj.port = comPortVar
    serialObj.baudrate = 9600
    serialObj.open()

for onePort in ports:
    comButton = Button(root, text=onePort, font=('Calibri', '13'), height=1, width=45, command = functools.partial(initComPort, index = ports.index(onePort)))
    comButton.grid(row=ports.index(onePort), column=0)

dataCanvas = Canvas(root, width=600, height=400, bg='white')
dataCanvas.grid(row=0, column=1, rowspan=100)

vsb = Scrollbar(root, orient='vertical', command=dataCanvas.yview)
vsb.grid(row=0, column=2, rowspan=100, sticky='ns')

dataCanvas.config(yscrollcommand = vsb.set)

dataFrame = Frame(dataCanvas, bg="white")
dataCanvas.create_window((10,0),window=dataFrame,anchor='nw')

def checkSerialPort():
    if serialObj.isOpen() and serialObj.in_waiting:
        recentPacket = serialObj.readline()
        recentPacketString = recentPacket.decode('utf').rstrip('\n')
        Label(dataFrame, text=recentPacketString)

while True:
    root.update()
    checkSerialPort()
    dataCanvas.config(scrollregion=dataCanvas.bbox("all"))