I'm trying to make my data analysis and reports less eye stabbing and more graphical with automatically generated graph-files, and to do this I've been playing with matplotlib/pyplot/pylab. Works brilliantly, but when I try to run it on a headless server...
tkinter.TclError: no display name and no $DISPLAY environment variable
For this application I only use PyLab, but after a little google, I added the below to before the pylab import:
import matplotlib
matplotlib.use("Agg")
Which should have changed the backend, but to no effect.
Any ideas what I'm doing wrong?
The remote machine does have X-forwarding capabilities, but since this application shouldn't NEED to display anything, I believe the usual ssh -X hack is overkill.
Examples:Fiendish Deception
Example working code on same machine
import matplotlib
matplotlib.use("Agg")
import numpy as np
import pylab as pl
xvals=np.arange(100)
yvals=np.cumsum(np.random.random(100))
yvals[-10:]=0
yvals=np.log(yvals)
pl.close()
pl.plot(xvals,yvals)
pl.xlabel("X")
pl.ylabel("Y")
pl.title("Title")
pl.savefig("testgraph.png")
Non-working real code
import matplotlib
matplotlib.use("Agg")
import numpy as np
import pylab as pl
import utility as util
import os
... non graph stuff...
def graph_p(self):
pl.close()
channels=range(self.p.shape[0])
for line in range(self.p.shape[1]):
yvals=np.ma.masked_invalid(map(util.watts_to_dbmhz,self.p[:,line]))
pl.plot(channels,yvals) #Error says it occurs here
pl.xlabel("Subchannel Index")
pl.ylabel("Power (dbmhz)")
pl.title("Plot of per-tone power assignments for %d lines"%self.p.shape[1])
pl.savefig(self.dest+self.scenario+'-power.png')
Nothing else touches pyplot.
Everything you describe sounds correct. What happens when you run this:
import matplotlib
matplotlib.use('Agg')
import pylab
pylab.plot([1,2], [3,4], linestyle='-')
pylab.savefig('foo.png')
In my environment it produces this (I scaled it down):
Try importing matplotlib
and setting the Agg
backend before importing numpy:
import matplotlib
matplotlib.use("Agg")
Turns out a utility file (not mine!) was pulling in pylab
for something else. Shifted the matplotlib
backend selection into the initial page.
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