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

Issue

Python scripts using Matplotlib fail on a server with the error "no display name and no $DISPLAY environment variable" when generating plots. The issue arises because Matplotlib utilizes the Xwindows backend by default and is incompatible with server environments that lack a graphical user interface (GUI).

Solution

To resolve this issue, set Matplotlib to use a non-interactive backend. There are several methods to achieve this:

1. Add Code to Script: At the beginning of your script, before importing matplotlib.pyplot, include the following code:

import matplotlib
matplotlib.use('Agg')

2. Modify Matplotlib Configuration File: In the file .config/matplotlib/matplotlibrc, add the line backend: Agg. This will instruct Matplotlib to use the non-interactive Agg backend.

echo "backend: Agg" > ~/.config/matplotlib/matplotlibrc

3. Use SSH with X Forwarding: When connecting to the server via SSH, use the -X option to enable Xwindows forwarding. This will allow GUI applications running on the server to interact with the client's GUI environment.

ssh -X remoteMachine.com

4. Export $DISPLAY Variable: Set the $DISPLAY environment variable to an appropriate value, such as the IP address and display number of the client's machine.

export DISPLAY=mymachine.com:0.0

By implementing one of these solutions, you can configure Matplotlib to operate in a server environment without relying on a GUI.