matplotlib 3.5.1

>>> """
===========
Close Event
===========

Example to show connecting events that occur when the figure closes.
"""
... import matplotlib.pyplot as plt
... 
... 
... def on_close(event):
...  print('Closed Figure!')
... 
... fig = plt.figure()
... fig.canvas.mpl_connect('close_event', on_close)
... 
... plt.text(0.35, 0.5, 'Close Me!', dict(size=30))
... plt.show()
...