two-vars.py

import tkinter as tk
import requests
import json
import time

class App:
      def __init__(self, master):
            self.frame = tk.Frame (master)
            self.frame.pack()
            self.variable_a = tk.StringVar()
            self.label1 = tk.Label(self.frame, textvariable=self.variable_a, width=20, height=10, relief="solid")
            self.label1.pack(side="left")
            self.variable_b = tk.StringVar()
            self.label2 = tk.Label(self.frame, textvariable=self.variable_b, width=20, height=10, relief="solid")
            self.label2.pack(side="right")

      def update_variables (self):
            response = requests.get("http://hipme.com/foo.json")
            if response.status_code==200:
                  data = json.loads(response.text)
                  self.variable_a.set(data["a"])
                  self.variable_b.set(data["b"])
            else:
                  self.variable_a.set("FAILED")
                  self.variable_b.set(response.status_code)

root = tk.Tk()
app = App(root)
last_time=0
while True:
      now = time.time()
      #import pdb; pdb.set_trace() 
      if now - last_time >= 1.0:
            app.update_variables() 
            last_time = now
      root.update_idletasks()
      root.update()

it might be better to use tk.mainloop and code the updates asynchronously, but it's more complex to explain
this version uses a bit of CPU in the loop, so the fan will run :-(