matplotlib.show() seemingly not doing anything

Question

I'm trying to get a simple python program to show a graph. I'm running Python 3.9 on Mac Catalina. My code is:

import numpy as np  
import matplotlib.pyplot as plt

x = np.linspace(1,120,120)
y = (2*10**-5)**2 + ((0.001)/(x))**2

plt.plot(x, y) 
plt.show()

I've tried following the instructions laid out in this: matplotlib hangs on mac osx and graph is not displayed

Namely, changing Interactive: False to Interactive: True in the matplotlibrc file, which didn't make any difference, and replacing:

import matplotlib.pyplot as plt with the following:

import matplotlib
matplotlib.use('TkAgg')
import matplotlib.pyplot as plt

But that hasn't worked either (I checked to see if the graph had gotten lost behind my terminal or anywhere else, and I couldn't find it so I'm assuming it hasn't showed).

In my matplotlibrc file, it has backend: Agg, but when I type matplotlib.get_backend() into my terminal whilst running Python, it returns "MacOSX". Given what it says in the matplotlibrc,

## ***************************************************************************
## * BACKENDS                                                                *
## ***************************************************************************
## The default backend.  If you omit this parameter, the first working
## backend from the following list is used:
##     MacOSX Qt5Agg Gtk3Agg TkAgg WxAgg Agg
## Other choices include:
##     Qt5Cairo GTK3Cairo TkCairo WxCairo Cairo
##     Qt4Agg Qt4Cairo Wx  # deprecated.
##     PS PDF SVG Template
## You can also deploy your own backend outside of matplotlib by referring to
## the module name (which must be in the PYTHONPATH) as 'module://my_backend'.
#backend: Agg

should this not be returning "Agg"?

I downloaded both numpy and matplotlib using pip3, and I'd prefer not to use Anaconda if possible, as I seem to have messed up my Windows machine installing and uninstalling there, but that is part of a different question.

When I copy and paste my code directly into the terminal running Python, my graph shows, which I suppose solves the problem of my graph not showing, but then I still have the problem if I want to run longer pieces of code, which would be my next step, as I eventually want to import a graph from matlab and compare it to this plot.

If I change my code to include the solution from the link above, so that my code reads:

import numpy as np  
import matplotlib
matplotlib.use('TkAgg')
print(matplotlib.get_backend())
import matplotlib.pyplot as plt

x = np.linspace(1,120,120)
y = (2*10**-5)**2 + ((0.001)/(x))**2

plt.plot(x, y) 
plt.show()

It outputs TkAgg, but then still doesn't show my graph. Why is this happening, and what can I do to fix it so that I can make graphs without copying and pasting into the terminal?