相关疑难解决方法(0)

我正在尝试将networkx与Python一起使用.当我运行此程序时,它会收到此错误.有什么遗漏？

#!/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, …

以下是我正在编写的代码的精简版本,以制作带有多个子图的图形.问题出现在最后一行,fig.savefig("foo" + ".pdf", format='pdf').我收到以下错误:

AttributeError: "'NoneType' object has no attribute 'print_figure'"

谁能告诉我什么是错的？谢谢!

import matplotlib.pyplot as plt
from pdb import set_trace as st
import numpy as np


Time   = np.array([0,1,2,3,4])
Load   = np.array([1,2,3,4,5])
Cell   = np.array([6,9,2,5,4])

axialLoadDueToCellPressure = 5.5 * Cell

volumePlotFormat = 'double-wide'

fig = plt.Figure()
ax1 = plt.subplot2grid((3,2), (0,0))


ax1.plot((Time/1000/60),
    (Load + axialLoadDueToCellPressure)/6, 'k-')

ax1.plot((Time/1000/60), Cell, 'k--')

st()
fig.savefig("foo" + ".pdf", format='pdf')