title: Running three Tkinter applications from single file
body: <p>I want to run 3 python file that contains Tkinter application for each one of them.
  The issue that 3 files located in 3 different locations on the PC.</p>
  <p>I succeeded to put the files in 2 functions that run when it called but the problem that when I run the script it waits for the first Tkinter window to close and then runs the rest application.</p>
  <p>The code :</p>
  <pre><code>def openRegisterApplication():
      os.chdir(dirsFolderToChdir['GUI'])
      os.system(f'python {expectedRegister_Application}')
  def openBackEnd():
      os.chdir(dirsFolderToChdir['FaceR'])
      os.system(f'python {expectedFaceR_cam_1} &amp; python {expectedGUI_Deshboard}')
  Thread(target = openRegisterApplication()).start()
  Thread(target = openBackEnd()).start()
  </code></pre>