Pyplot “cannot connect to X server localhost:10.0” despite ioff() and matplotlib.use('Agg')

问题

I have a piece of code which gets called by a different function, carries out some calculations for me and then plots the output to a file. Seeing as the whole script can take a while to run for larger datasets and since I may want to analyse multiple datasets at a given time I start it in screen then disconnect and close my putty session and check back on it the next day. I am using Ubuntu 14.04. My code looks as follows (I have skipped the calculations):

import shelve
import os, sys, time
import numpy
import timeit
import logging
import csv
import itertools

import graph_tool.all as gt
import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as plt

plt.ioff()

#Do some calculations

print 'plotting indeg'      
# Let's plot its in-degree distribution
in_hist = gt.vertex_hist(g, "in")

y = in_hist[0]
err = numpy.sqrt(in_hist[0])
err[err >= y] = y[err >= y] - 1e-2

plt.figure(figsize=(6,4))
plt.errorbar(in_hist[1][:-1], in_hist[0], fmt="o",
        label="in")
plt.gca().set_yscale("log")
plt.gca().set_xscale("log")
plt.gca().set_ylim(0.8, 1e5)
plt.gca().set_xlim(0.8, 1e3)
plt.subplots_adjust(left=0.2, bottom=0.2)
plt.xlabel("$k_{in}$")
plt.ylabel("$NP(k_{in})$")
plt.tight_layout()
plt.savefig("in-deg-dist.png")
plt.close()

print 'plotting outdeg'

#Do some more stuff

The script runs perfectly happily until I get to the plotting commands. To try and get to the root of the problem I am currently running it in putty without screen and with no X11 applications. The ouput I get is the following:

plotting indeg
PuTTY X11 proxy: unable to connect to forwarded X server: Network error: Connection refused
: cannot connect to X server localhost:10.0

I presume this is caused by the code trying to open a window but I thought that by explicitely setting plt.off() that would be disabled. Since it wasn't I followed this thread (Generating matplotlib graphs without a running X server ) and specified the backend, but that didn't solve the problem either. Where might I be going wrong?

回答1:

The calling function calls other functions too which also use matplotlib. These get called only after this one but during the import statement their dependecies get loaded. Seeing as they were loaded first they disabled the subsequent matplotlib.use('Agg') declaration. Moving that declaration to the main script has solved the problem.

来源：https://stackoverflow.com/questions/38612473/pyplot-cannot-connect-to-x-server-localhost10-0-despite-ioff-and-matplotlib