pydotplus.graphviz.InvocationException: GraphViz's executables not found

    sklearn决策树可视化时报错（graph.write_png()），出错原因是没有安装GraphViz's executables。Graphviz不是一个python tool，仍然需要安装GraphViz's executables.下载链接 http://www.graphviz.org/download/

    对于一般IDE环境下安装后需要将Graphviz的bin路径添加到环境变量Path中，对于虚拟环境，例如conda，需要将bin路径下的内容拷贝到虚拟环境下的Library目录下（重复不覆盖）。

import pydotplus
import collections
data_feature_names = [']
# dot_data = export_graphviz(clf_DT, out_file='tree.dot')
dot_data = export_graphviz(clf_DT,
                           feature_names=data_feature_names,
                           out_file=None,
                           filled=True,
                           rounded=True)
graph = pydotplus.graph_from_dot_data(dot_data)

colors = ('turquoise', 'orange')
edges = collections.defaultdict(list)

for edge in graph.get_edge_list():
    edges[edge.get_source()].append(int(edge.get_destination()))

for edge in edges:
    edges[edge].sort()
    for i in range(2):
        dest = graph.get_node(str(edges[edge][i]))[0]
        dest.set_fillcolor(colors[i])
graph.write_png('tree.png')

Refs:

http://www.cnblogs.com/iamxyq/p/5919179.html

https://stackoverflow.com/questions/18438997/why-is-pydot-unable-to-find-graphvizs-executables-in-windows-8