Save matplotlib figures and save to a server

On my personal computer I have created many figures with matplotlib. I've always used  plt.show() to show the figures and plt.savefig() to save the images, but I've had a lot of trouble saving a figure onto the server. 
At work, python is installed on the server, but saving the figures has never worked. I always get the error no display name and no $DISPLAY environment variable
Turns out I was just missing a single line of code. After importing matplotlib type mpl.use('Agg'). This will fix the problem.

Example:

import matplotlib as mpl
mpl.use('Agg')   #Not sure why, but this makes saving to a server possible.
import matplotlib.pyplot as plt
import numpy as np

x = np.arange(0,50,.2)
y = np.sin(x)

plt.plot(x,y)
plt.title("This works!!! I'm so excited")
plt.savefig(path to save image + image_name.png)
plt.close()

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