RuntimeError: The 'Agg' backend does not support show()

RuntimeError: The ‘Agg’ backend does not support show()

$ python -c "import matplotlib; matplotlib.use('Agg'); import matplotlib.pyplot as plt; plt.show()"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
RuntimeError: The 'Agg' backend does not support show()

Why this happens

Agg renders to images only; it cannot display GUI windows.

Fix

Use savefig or switch to a GUI backend.

Wrong code

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
plt.show()

Fixed code

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt
plt.plot([1,2,3])
plt.savefig('plot.png')