Exception: "dot" not found in path in python on mac

I want to use `caffe.draw` to draw the caffe net by anaconda python on mac. But I got the error like this: ``` File "python/draw_net.py", line 45, in <module> main() File "python/draw_net.py", line 41, in main caffe.draw.draw_net_to_file(net, args.output_image_file, args.rankdir) File "/Users/xxh/caffe/distribute/python/caffe/draw.py", line 222, in draw_net_to_file fid.write(draw_net(caffe_net, rankdir, ext)) File "/Users/xxh/caffe/distribute/python/caffe/draw.py", line 204, in draw_net return get_pydot_graph(caffe_net, rankdir).create(format=ext) File "/Users/xxh/anaconda2/lib/python2.7/site-packages/pydot.py", line 1883, in create prog=prog)) Exception: "dot" not found in path. ``` I have installed pydot and graphviz ,and how can I add the dot's path to python path?