"UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure." when plotting figure with pyplot on Pycharm

Question

I am trying to plot a simple graph using pyplot, e.g.:

import matplotlib.pyplot as plt
plt.plot([1,2,3],[5,7,4])
plt.show()

but the figure does not appear and I get the following message:

UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.

I saw in several places that one had to change the configuration of matplotlib using the following:

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

I did this, but then got an error message because it cannot find a module:

ModuleNotFoundError: No module named 'tkinter'

Then, I tried to install "tkinter" using pip install tkinter (inside the virtual environment), but it does not find it:

Collecting tkinter
  Could not find a version that satisfies the requirement tkinter (from versions: )
No matching distribution found for tkinter

I should also mention that I am running all this on Pycharm Community Edition IDE using a virtual environment, and that my operating system is Linux/Ubuntu 18.04.

I would like to know how I can solve this problem in order to be able to display the graph.

Answer 1

I found a solution to my problem (thanks to the help of ImportanceOfBeingErnest).

All I had to do was to install tkinter through the Linux bash terminal using the following command:

sudo apt-get install python3-tk

instead of installing it with pip or directly in the virtual environment in Pycharm.