python找不到路径_（Python）ValueError：在路径中找不到程序点

I have the following problem: I am on xUbuntu OS and I am trying to use networkx in a Flask application, and I am having the following code:

.....

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')

The last line is line 411. I get the following error:

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.

What could be causing this problem? I've installed networkx and pygraphviz, but I still get this error. Any ideas how to solve this problem?

解决方案

PyGraphviz doesn't work without Graphviz. Install that too.