Resolving "_tkinter.TclError: no display name and no $DISPLAY environment variable" Error

When executing a Python script involving Matplotlib on a server, you may encounter the error "_tkinter.TclError: no display name and no $DISPLAY environment variable." This error arises because Matplotlib defaults to using the Xwindows backend, which requires a graphical display environment. However, server environments often lack this capability.

To address this issue, you can instruct Matplotlib to utilize a non-interactive backend instead. Insert the following code at the beginning of your script, before importing pyplot:

import matplotlib
matplotlib.use('Agg')

Alternatively, you can add the following line to the .config/matplotlib/matplotlibrc file:

backend: Agg

This will configure Matplotlib to use the Agg backend, which does not require a graphical display.

Another option is to use ssh with X11 forwarding:

ssh -X remoteMachine

This command allows you to access Xwindows applications remotely.

Finally, you can set the DISPLAY environment variable:

export DISPLAY=mymachine.com:0.0

By specifying a valid display name, Matplotlib will be able to connect to a graphical display on another machine.

For further information, refer to the Matplotlib FAQ: https://matplotlib.org/faq/howto_faq.html#matplotlib-in-a-web-application-server