Suppose I have some third-party code main.py:

import matplotlib.pyplot as plt
import tkinter

tk = tkinter.Tk()

fig = plt.figure()
ax = plt.gca()
ax.plot([1,2,3])
plt.savefig('test.png')

Suppose that, in order to test this code, I need to creat a mock Tk class and replace the definition in main with it in a file called mock_main.py:

import tkinter

class Tk:
  pass

tkinter.Tk = Tk

import main

Now, if I run python mock_main.py, I get an error:

Traceback (most recent call last):
  File "C:\Users\user\desktop\temp\compare_mpl_backends\mock_main.py", line 8, in <module>
    import main
  File "C:\Users\user\desktop\temp\compare_mpl_backends\main.py", line 6, in <module>
    fig = plt.figure()
  File "C:\Users\user\Miniconda3\envs\temp\lib\site-packages\matplotlib\pyplot.py", line 787, in figure
    manager = new_figure_manager(
  File "C:\Users\user\Miniconda3\envs\temp\lib\site-packages\matplotlib\pyplot.py", line 306, in new_figure_manager
    return _backend_mod.new_figure_manager(*args, **kwargs)
  File "C:\Users\user\Miniconda3\envs\temp\lib\site-packages\matplotlib\backend_bases.py", line 3494, in new_figure_manager
    return cls.new_figure_manager_given_figure(num, fig)
  File "C:\Users\user\Miniconda3\envs\temp\lib\site-packages\matplotlib\backends\_backend_tk.py", line 925, in new_figure_manager_given_figure
    window = tk.Tk(className="matplotlib")
TypeError: Tk() takes no arguments

I understand why this error occurs. matplotlib also depends on tkinter.Tk, so when I override it in mock_main.py, it basically breaks the matplotlib code.

I want to leave matplotlib alone, namely allowing it to use the true definition of Tk. However, for the third party code main.py, I want to use my (mock) definition.

Is there any elegant way to achieve this in python without modifying the contents of main.py?