tkinter window doesn't open until mainloop() is invoked

[djaychela]

I'm seeing a difference in behaviour between the python REPL and bpython.

When running this as two lines in the REPL:

import tkinter as tk
window = tk.Tk()

On python 3.12 (and I believe earlier) as soon as the window is created, it appears.

On bpython running the code makes a separate python app appear (i.e Python appears at the top left of the screen), but there's no window. If I look in 'force quit' then Python says it's not responding.

However, I can get the window to appear by calling window.mainloop(). In addition when this is called, Python no longer appears as 'not responding' in the Force Quit window.