title: How to update the ttk progress bar on tkinter
body: <p>I've got a program that does some simple webscraping. I'm working on giving it to my coworkers to use, but they are unfamiliar with code so I'd like to make a GUI. I've started using tkinter, and I'm currently working on making a progress bar showing where the program is at (it can take up to a couple hours to run). My problem is that I can't seem to get the progress bar to update, and all the online sources use Tkinter, which is an old version. Here is my code:</p>
  
  <p>I've tried updating progressBar['value'] to whatever number I want, but that hasn't been working. </p>
  
  <pre><code>from tkinter import *
  from tkinter import ttk
  import time
  
  
  def clicked(progressBar): # runs a couple functions and updates the progress bar when the button is clicked
      num = 0
      for item in range(5):
          # functions go here
          num += 10
          progressBar['value'] = num
          time.sleep(2)
  
  window = Tk()
  window.title("Welcome to my app")
  window.geometry('600x400')
  
  progressBar = ttk.Progressbar(window, orient='horizontal', length=300, mode='determinate', maximum=100, value=0)
  progressBar.grid(columnspan=3, row=2, sticky=(W, E))
  
  btn = Button(window, text="Click me!", command=clicked(progressBar))
  btn.grid(column=1, row=1)
  
  window.mainloop()
  </code></pre>
  
  <p>The tkinter window doesn't open up until 10 seconds after I run the program, and it has the progress bar already at 50% full. I'd like for the bar to slowly increment up, AFTER the button has been clicked. Any advice would be helpful! Thank you!</p>