Question

I ran into a python error that i have been trying to solve for several days now.
My program creates figures, saves and closes them which works fine except for this error. Usually it does not hinder the saving process but sometimes a picture is missing the lower part when saved. The odd thing is that this only happens every second time the loop reaches the savefig method, here is my code:

for num in np.arange(file_number):
    plt.figure('abc' + str(num),figsize=(22,12),dpi=100)
    #some plots are added to the figure
    print 1
    plt.savefig(os.path.join(savepath,filename),dpi=100)
    print 2
    plt.close()                                                                    
    print 3

I use the print commands to see where the error occurs. Here is the console output of spyder:

Reading file1.file
1
2
3
Reading file2.file
1
Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/matplotlib/backends/backend_qt4.py", line 151, in <lambda>
    lambda: self.close_event())
  File "/usr/lib/pymodules/python2.7/matplotlib/backend_bases.py", line 1564, in close_event
    self.callbacks.process(s, event)
RuntimeError: underlying C/C++ object has been deleted
2
3
Reading file3.file
1
2
3
Reading file4.file
1
Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/matplotlib/backends/backend_qt4.py", line 151, in <lambda>
    lambda: self.close_event())
  File "/usr/lib/pymodules/python2.7/matplotlib/backend_bases.py", line 1564, in close_event
    self.callbacks.process(s, event)
RuntimeError: underlying C/C++ object has been deleted
2
3

To my understanding, the error already occurs while saving the figure (every second time), although it works fine if i omit the close() command. In that case, my RAM is filled after about 70 files and sometimes i need to evaluate a couple of hundreds. That’s why i need to include the close() command or something similar.
If you solve this (or improve my programing, i guess the way i did this saving and closing might be considered ugly) please help me.

Answer 1

How about change the backend to other options? For example:

import matplotlib as mpl
mpl.use( "agg" )

from matplotlib import pyplot as plt
import numpy as np

print plt.get_backend()

file_number = 100
for num in np.arange(file_number):
    plt.figure('abc' + str(num),figsize=(22,12),dpi=100)
    #some plots are added to the figure
    print 1
    plt.savefig("%d.png" % num,dpi=100)
    print 2
    plt.close()
    print 3