import serial
import os
from tkinter import *
class okno():
     def __init__ (self):
          global dat
          dat = StringVar()
          lab1 = Label(root, text = t, font="Arial 22",)
          lab2 = Label(root, text = "Температура", font="Arial 18",)
          but = Button(root, text="SEND", width=8, height=5)
          ent = Entry(root,textvariable = dat, width=20, bd=3)
          lab1.grid(row=0, column=0)
          lab2.grid(row=1, column=0)
          but.grid(row=0, column=1)
          ent.grid(row=1, column=1)
          but.bind("<Button-1>", self.send)
          ent["textvariable"] = dat
         
     def send (self, event):
          dat1 = str(dat.get())
          print (dat1)
          ser = serial.Serial('COM1', 9600)
          data = (bytes(dat1, encoding='ascii'))
          ser.write (data)
          
     def temp ():
          ser = serial.Serial('COM1', 9600)
          s=str(ser.readline())
          s=s[2:5]     
          return s
t = okno.temp()    
root = Tk()
root.title("Terminal")
root.geometry('300x200')
root.maxsize(300, 200)
obj = okno()

from Tkinter import *
import time
def tick():
    label.after(200, tick)
    label['text'] = time.strftime('%H:%M:%S')
root=Tk()
label = Label(font='sans 20')
label.pack()
label.after_idle(tick)
root.mainloop()