（Python）ValueError：在路径中找不到程序点

Question

我有以下问题：我在xUbuntu OS上，并且试图在Flask应用程序中使用networkx，并且我有以下代码：

.....
import networkx as nx
......
# Creating and initializing graph object which is networkx object
hosts_graph = get_networkx_graph_object()

# Variable 'coord' where the coordinates for each node will be stored
coord = nx.pygraphviz_layout(hosts_graph, prog = 'dot')

最后一行是第411行。出现以下错误：

File "/home/kiril/Documents/workfolder/omeganoc-sprint/onoc/omeganoc/grapher.py", line 411, in grouping_method
    coord = nx.pygraphviz_layout(hosts_graph, prog = 'dot')
  File "/usr/local/lib/python2.7/dist-packages/networkx-1.7-py2.7.egg/networkx/drawing/nx_agraph.py", line 264, in pygraphviz_layout
    A.layout(prog=prog,args=args)
  File "/usr/local/lib/python2.7/dist-packages/pygraphviz-1.1-py2.7-linux-x86_64.egg/pygraphviz/agraph.py", line 1301, in layout
    data=self._run_prog(prog,' '.join([args,"-T",fmt]))
  File "/usr/local/lib/python2.7/dist-packages/pygraphviz-1.1-py2.7-linux-x86_64.egg/pygraphviz/agraph.py", line 1248, in _run_prog
    runprog=self._get_prog(prog)
  File "/usr/local/lib/python2.7/dist-packages/pygraphviz-1.1-py2.7-linux-x86_64.egg/pygraphviz/agraph.py", line 1236, in _get_prog
    raise ValueError("Program %s not found in path."%prog)
ValueError: Program dot not found in path.

是什么导致此问题？我已经安装了networkx和pygraphviz，但是仍然出现此错误。任何想法如何解决这个问题？

Answer 1

没有Graphviz，PyGraphviz不能工作。也安装。