How would I constantly update a variable within a script/program? - python-3.x

Question

I am attempting to make a thermostat of sorts. To do this, I am using a Pi3 with a DHT22 Temperature sensor, and Python3.
What I need is for the temperature to be polled and the corresponding variable to update on its own.
Attempting to do so with any sort of While True: statements results in the gui I'm testing with, not opening.
I'm lost (And yes, this code is hacked together from others. LOL)
#! python3
import time
import RPi.GPIO as GPIO
import string
import tkinter
import tkinter.ttk
import Adafruit_DHT
from tkinter import messagebox
from tkinter import *
root = Tk()
root.title('PiTEST')
root.configure(background='black')
GPIO.setmode(GPIO.BCM)
GPIO.setwarnings(False)
sensor = Adafruit_DHT.DHT22
pin = 4
def PRINTTEST():
print(temperature, humidity)
TESTTEXT = Label(root,text="TESTING",fg="white",bg="black",font='Consolas 20 bold')
TESTTEXT.grid(row=1,column=1,sticky="W,S,E")
B1 = tkinter.Button(root,bd=5,text="TEST",bg="gray",fg="white",command=PRINTTEST,height=4,width=20)
B1.grid(row=2,column=1,sticky="N,S,E,W",padx=8,pady=8)
while True:
humidity, temperature = Adafruit_DHT.read_retry(sensor, pin)
temperature = temperature * 9/5.0 + 32
root.mainloop()
GPIO.cleanup()

Answer 1

Here is a code example without your GPIO things:
#! python3
import time
import string
import tkinter
import random
from tkinter import messagebox
from tkinter import *
root = Tk()
root.title('PiTEST')
root.configure(background='black')
def PRINTTEST():
temperature = random.randint(0,100)
humidity = random.randint(0,100)
print(temperature, humidity)
root.after(1000, PRINTTEST)
TESTTEXT = Label(root,text="TESTING",fg="white",bg="black",font='Consolas 20 bold')
TESTTEXT.grid(row=1,column=1,sticky="W,S,E")
B1 = tkinter.Button(root,bd=5,text="TEST",bg="gray",fg="white",command=PRINTTEST,height=4,width=20)
B1.grid(row=2,column=1,sticky="N,S,E,W",padx=8,pady=8)
root.mainloop()
This will print 2 random integers every second in your terminal.