views:

358

answers:

3
+1  Q: 

python networkx

hi,

i am trying to use networkx with python, when i run this program, it get this error, is there anything missing?

#!/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

hi reinout,

thanks for that but, i get a different error now...for this code

#!/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
A: 

What system are you on? It looks like you have a system with X11, but the DISPLAY environment variable was not properly set. Try executing the following command and then rerunning your program:

export DISPLAY=localhost:0
Michael Aaron Safyan
but why does it eed to set a display variable, i am remotely logged on to this server, all it should do is generate a PNG file???
krisdigitx
@krisdigitx, if you are remotely connected, don't set a display variable; instead use the "-XY" flag when you connect. In order to display, it needs to know which Xserver to send the image to; in this case, it would be the display of your computer, instead of the remote computer. Using the "-XY" flag causes SSH to set the DISPLAY variable automatically to point to the display of the connecting computer.
Michael Aaron Safyan
@krisdigitx, I agree, it is very strange that it does that; my guess, though, is that it paints the image using X11, and then saves the result using X11.
Michael Aaron Safyan
+1  A: 

The main problem is that (on your system) matplotlib chooses an x-using backend by default. I just had the same problem on one of my servers. The solution for me was to add the following code in a place that gets read before any other pylab/matplotlib import:

import matplotlib
# Force matplotlib to not use any Xwindows backend.
matplotlib.use('Agg')

The alternative is to set it in your .matplotlibrc

Reinout van Rees
+1 for the `.use` to specify the backend.
Noufal Ibrahim
A: 

hi reinout,

thanks for that but, i get a different error now...for this code

#!/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
krisdigitx
This should be an edit to your question rather than a new answer.
Noufal Ibrahim