There seems to be a memory leak in tkinter on OSX (Windows and Linux don't seem to be affected). Explicitly calling Tk.update() sometimes permanently allocates a multiple of 4096 bytes. Allocation happens more frequently if update calls are in close succession.

import time
from tkinter import Tk
root = Tk()

while True:
    root.update()  # Huge memory leak

while True:
    root.update()  # No memory leaks
    time.sleep(1)

Issue occurs on python3.3 and above, did not test on older versions.

tkinter is pretty much just a thin wrapper around the Tcl/Tk C API so suspicion for behavior like this should start there.  Usually, the easiest way to confirm that is to write an equivalent test in Tcl using its wish shell but, in this case, there's an even easier way.  The memory leak is easy to see if you use the badly out-of-date and seriously flawed system Tcl/Tk 8.5.x supplied by Apple in OS X releases since 10.6.  If tkinter is linked with an up-to-date Tcl/Tk, the leak should go away.  At least that's the case when using python3.5 from python.org 10.6+ installers and with ActiveTcl 8.5.18 installed.  See https://www.python.org/download/mac/tcltk/ for more info.