Python Adventures

Problem
On a remote server of mine I wanted to create some nice figures with matplotlib. It worked well on localhost but it failed on the server. First, tkinter was missing. Second, there was a problem with $DISPLAY.

Solution
To install tkinter, check out this earlier post.

The second problem is caused by a missing X server. On a remote server usually there is no graphical interface. To solve it, just add these two lines to the top of your program:

import matplotlib as mpl
mpl.use('Agg')

Example
Before:

#!/usr/bin/env python3
# coding: utf-8

import pylab
import numpy as np

def main():
    x = np.arange(-3.14, 3.14, 0.01)
    y = np.sin(x)
    pylab.plot(x, y, "b")
    pylab.savefig("out.png")

##############################################################################

if __name__ == "__main__":
    main()

After:

#!/usr/bin/env python3
# coding: utf-8

import matplotlib as mpl
mpl.use('Agg')

import pylab
import numpy as np

def main():
    x = np.arange(-3.14, 3.14, 0.01)
    y = np.sin(x)
    pylab.plot(x, y, "b")
    pylab.savefig("out.png")

##############################################################################

if __name__ == "__main__":
    main()

Output: