pyplot.show() reopens old tkinter dialog

EDIT: This seems to be a problem restricted to Tcl/Tk on Mac OS systems. So if you have no experience with that, this topic might be moot...

I want to have a Python script that does two things:

Ask the user for a file name via a Tkinter file dialog.
Plot some data from said file.

The problem is, matplotlib uses Tkinter for the graphical representations, and whenever I call pyplot.show() in non-interactive mode, the (before closed) file dialog pops up again. It seems to me like pyplot.show() gathers a list of all Tkinter windows and shows them all. I did not find any help on this however. I tried for both Python 2.7 and 3.3, since a lot of the Tkinter module seems to have changed, but it's the same phenomenon. The slightly strange workaround I came up with is to go into matplotlib interactive mode and then keep the windows open with a raw_input() command.

Here is a minimal code snippet that works in Python 2 and 3 to show the problem:

import matplotlib.pyplot as plt

# import Tkinter GUI (changes from Python 2.x to 3.x)
try:
    import Tkinter
except (ImportError):
    import tkinter as Tkinter
try:
    from tkFileDialog import askopenfilename
except (ImportError):
    from tkinter.filedialog import askopenfilename

root = Tkinter.Tk()
root.withdraw()

input_filename = askopenfilename(master=root)

# This seemed promising, but it doesn't help
root.destroy()

plt.figure()

# uncommenting this to switch to interactive mode is a workaround
#plt.ion()
plt.show()

# Python 2.x and 3.x compatible wait for input:
try: input = raw_input
except NameError: pass
# Wait for keystroke (for interactive mode)
input("Press enter when done...")

I'm sorry if I'm missing something obvious here, I am not that well-versed in Python, and I did not find satisfying information on this problem. But my gutt tells me there has to be a simple and elegant solution for this.

System information (most recent versions I tried):