Current, working file

import subprocess, time, re, math, threading, queue
import PySimpleGUI as sg
from sys import platform

STEP_SIZE = 1
NO_OF_PINGS = 500
MAX_PING = 250
CANVAS_SIZE = (800, 600)

ping = ""

class justAList():
    def __init__(self):
        self.matchList = ['', '', '']


def main_loop(matchClass, gui_queue):
    lowestPing = averagePing = highestPing = totalPing = 0
    sg.change_look_and_feel('Dark Blue 3')
    inputLayout = [
        [sg.Text('Enter domain name of what you want to ping')],
        [sg.InputText(size=(37, 1), key='dn')],
        [sg.Submit(), sg.Cancel()]
    ]

    inputWindow = sg.Window('Domain name entry', inputLayout)
    event, value = inputWindow.read()
    if event is None or event == 'Cancel':
        return

    matchClass.matchList[0] = value['dn']
    if platform == 'darwin' or platform == 'linux' or platform == 'linux2':
        matchClass.matchList[1] = ''.join(re.findall('Ping statistics for (\d+.\d+.\d+.\d+)', subprocess.run(['ping', '-c', '1', matchClass.matchList[0]], capture_output=True).stdout.decode()))
    elif platform == 'win32':
        matchClass.matchList[1] = ''.join(re.findall('Ping statistics for (\d+.\d+.\d+.\d+)', subprocess.run(['ping', '-n', '1', matchClass.matchList[0]], capture_output=True).stdout.decode()))

    inputWindow.close()
    del inputWindow

    sg.set_options(element_padding=(0,0))

    sg.change_look_and_feel('Dark Blue 3')
    graphLayout = [
        [sg.Text("          The IP address of hostname '" + matchClass.matchList[0] + "' is: " + matchClass.matchList[1], size=(100, 1), )],
        [sg.Text("")],
        [sg.Text("Ping\n(ms)", size=(5, 2)), sg.Graph((20, 600), (0, 0), (20, MAX_PING), background_color='white', key='yAxis'),
        sg.Graph(CANVAS_SIZE, (0, 0), (NO_OF_PINGS, MAX_PING), background_color='white', key='mainGraph')],
        [sg.Text(size=(5, 1)), sg.Graph((822, 20), (0, 0), (NO_OF_PINGS, 20), background_color='white', key='xAxis')],
        [sg.Text("          Number of pings: 0\t\t", key='nP'), sg.Text("Lowest ping: " + str(lowestPing) + '\t\t', key='lP'),
        sg.Text("Average ping: " + str(averagePing) + '\t\t', key='aP'), sg.Text("Highest ping: " + str(highestPing), key='hP')],
        [sg.Button('Exit', button_color=('black', 'white'))]
    ]

    graphWindow = sg.Window(matchClass.matchList[0], graphLayout, grab_anywhere=True, no_titlebar=False, use_default_focus=False, finalize=True)
    mainGraph = graphWindow['mainGraph']
    xGraph = graphWindow['xAxis']
    yGraph = graphWindow['yAxis']


    yGraph.DrawLine((20, 0), (20, MAX_PING))
    xGraph.DrawLine((13, 19), (NO_OF_PINGS, 19))

    for x in range(20, NO_OF_PINGS - 1, 20):
        xGraph.DrawLine((x, 10), (x, 20))
        if x != 0:
            xGraph.DrawText(x, (x, 5), color='green')

    for y in range(20, MAX_PING - 1, 20):
        yGraph.DrawLine((10, y), (20, y))
        if y != 0:
            yGraph.DrawText(y, (10, y-3), color='blue')

    threading.Thread(target=ping, args=(10, gui_queue, matchClass), daemon=True).start()

    i, j = 0, 1
    prev_x, prev_y = 0, 0
    graph_value = 0

    while True:
        graph_value = 0
        event, values = graphWindow.read(timeout=25)
        if event == 'Exit' or event is None:
            break

        while True:
            try:
                graph_value = gui_queue.get_nowait()
            except queue.Empty:
                break

        if graph_value > 0:

            if j == 1:
                lowestPing = averagePing = highestPing = graph_value
            else:
                if lowestPing > graph_value:
                    lowestPing = graph_value
                if highestPing < graph_value:
                    highestPing = graph_value
            totalPing += graph_value
            averagePing = '{:.2f}'.format(totalPing / j, 2)

            graphWindow['nP'].Update("          Number of pings: " + str(j) + '\t\t')
            graphWindow['lP'].Update("Lowest ping: " + str(lowestPing) + '\t\t')
            graphWindow['aP'].Update("Average ping: " + averagePing + '\t')
            graphWindow['hP'].Update("Highest ping: " + str(highestPing))

            #print("Iteration #" + str(j) + " - highest ping is " + str(highestPing))

            if graph_value > MAX_PING:
                graph_value = MAX_PING
            if graph_value < 0:
                graph_value = 0

            new_x, new_y = i, graph_value

            if i >= NO_OF_PINGS:
                mainGraph.move(-STEP_SIZE, 0)
                prev_x = prev_x - STEP_SIZE

            mainGraph.draw_line((prev_x, prev_y), (new_x, new_y), color='red')
            prev_x, prev_y = new_x, new_y
            i += STEP_SIZE if i < NO_OF_PINGS else 0
            j += 1

    graphWindow.close()
    del graphWindow

def ping(run_freq, gui_queue, matchClass):
    while True:
        try:
            time.sleep(run_freq/1000)
            ping = ""
            if platform == 'darwin' or platform == 'linux' or platform == 'linux2':
                ping = subprocess.run(['ping', '-c', '1', matchClass.matchList[0]], capture_output=True, text=True)
            elif platform == 'win32':
                ping = subprocess.run(['ping', '-n', '1', matchClass.matchList[0]], capture_output=True, text=True)
            cmdOutput = ''.join(re.findall('time=(\d+)', ping.stdout))
            if cmdOutput.isdigit() == True:
                gui_queue.put(int(cmdOutput))
        except ValueError:
            continue


if __name__ == '__main__':
    matchClass = justAList()

    gui_queue = queue.Queue()

    main_loop(matchClass, gui_queue)