Problem
I’m attempting to use Python with networkx. This error occurs when I execute this software. Is there anything else you’d like to add?
#!/usr/bin/env python
import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt
G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")
Traceback (most recent call last):
File "graph.py", line 13, in <module>
nx.draw(G)
File "/usr/lib/pymodules/python2.5/networkx/drawing/nx_pylab.py", line 124, in draw
cf=pylab.gcf()
File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
return figure()
File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
**kwargs)
File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
window = Tk.Tk()
File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable
Now I’m getting a different error:
#!/usr/bin/env python
import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt
matplotlib.use('Agg')
G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")
/usr/lib/pymodules/python2.5/matplotlib/__init__.py:835: UserWarning: This call to matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.
if warn: warnings.warn(_use_error_msg)
Traceback (most recent call last):
File "graph.py", line 15, in <module>
nx.draw(G)
File "/usr/lib/python2.5/site-packages/networkx-1.2.dev-py2.5.egg/networkx/drawing/nx_pylab.py", line 124, in draw
cf=pylab.gcf()
File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
return figure()
File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
**kwargs)
File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
window = Tk.Tk()
File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable
Now I’m getting a different error:
#!/usr/bin/env python
import networkx as nx
import matplotlib
import matplotlib.pyplot
import matplotlib.pyplot as plt
matplotlib.use('Agg')
G=nx.Graph()
G.add_node(1)
G.add_nodes_from([2,3,4,5,6,7,8,9,10])
#nx.draw_graphviz(G)
#nx_write_dot(G, 'node.png')
nx.draw(G)
plt.savefig("/var/www/node.png")
/usr/lib/pymodules/python2.5/matplotlib/__init__.py:835: UserWarning: This call to matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,
or matplotlib.backends is imported for the first time.
if warn: warnings.warn(_use_error_msg)
Traceback (most recent call last):
File "graph.py", line 15, in <module>
nx.draw(G)
File "/usr/lib/python2.5/site-packages/networkx-1.2.dev-py2.5.egg/networkx/drawing/nx_pylab.py", line 124, in draw
cf=pylab.gcf()
File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 276, in gcf
return figure()
File "/usr/lib/pymodules/python2.5/matplotlib/pyplot.py", line 254, in figure
**kwargs)
File "/usr/lib/pymodules/python2.5/matplotlib/backends/backend_tkagg.py", line 90, in new_figure_manager
window = Tk.Tk()
File "/usr/lib/python2.5/lib-tk/Tkinter.py", line 1650, in __init__
self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable
Asked by krisdigitx
Solution #1
The fundamental issue is that matplotlib defaults to utilizing an x-based backend (on your machine). On one of my servers, I recently encountered the identical issue. For me, the solution was to place the following code in a location where it would be read before any other pylab/matplotlib/pyplot import:
import matplotlib
# Force matplotlib to not use any Xwindows backend.
matplotlib.use('Agg')
Set it in your as an alternative. matplotlibrc
Answered by Reinout van Rees
Solution #2
As a complement to Reinout’s response.
Editing the.matplotlibrc file is the only permanent solution to this problem. It can be found by going to
>>> import matplotlib>>> matplotlib.matplotlib_fname()
# This is the file location in Ubuntu
'/etc/matplotlibrc'
Then, in that file, change the backend to backend: Agg. That is all there is to it.
Answered by Chris.Q
Solution #3
The simple solution is to spend some time properly preparing your execution environment.
The first step in preparing your execution environment is to use a matplotlibrc file, which Chris Q. has rightly recommended.
backend : Agg
in that particular file You may even alter how and where matplotlib looks for and discovers the matplotlibrc file without changing any code.
The second method for preparing your execution environment is to utilize the MPLBACKEND environment variable (and make sure your users know about it):
export MPLBACKEND="agg"
python <program_using_matplotlib.py>
This is convenient because you do not need to give another file on disk for this to work. I’ve used this strategy for testing in continuous integration and running on remote PCs without displays, for example.
Hard-coding your matplotlib backend to “Agg” in your Python code is akin to hammering a square peg into a round hole when you could simply tell matplotlib that it needs to be a square hole.
Answered by gotgenes
Solution #4
When I tried to use matplotlib with Spark, I got an error. For some reason, matplotlib.use(‘Agg’) does not work for me. Finally, I found that the code below works for me. More information can be found here.
import matplotlib.pyplot as plt.
plt.switch_backend('agg')
Answered by user3282611
Solution #5
I’ll just restate what @Ivo Bosticky said, which is easily forgotten. These lines should go at the very beginning of the py file.
import matplotlib
matplotlib.use('Agg')
Otherwise, an error would occur.
*/usr/lib/pymodules/python2.7/matplotlib/__init__.py:923: UserWarning: This call to matplotlib.use() has no effect
because the the backend has already been chosen;
matplotlib.use() must be called *before* pylab, matplotlib.pyplot,*
All Display issues will be resolved as a result of this.
Answered by Somum
Post is based on https://stackoverflow.com/questions/2801882/generating-a-png-with-matplotlib-when-display-is-undefined