各位大神：

我在window系统已经安装好Graphviz，但是在python里面运行如下语句：

plot_tree(clf, num_trees=0)， 系统报错如下：

ExecutableNotFound: failed to execute ['dot', '-Tpng'], make sure the Graphviz executables are on your systems' PATH

所有的工作感觉都做了，包括安装Graphviz，配置环境变量，不知道问题出在哪里，跪谢大神！

你还要pip install pydot
如果还是有错，需要在pydot.py文件中修改
def set_prog(self, prog):
        """Sets the default program.

        Sets the default program in charge of processing
        the dot file into a graph.
        """
        #path = r'C:/Program File (x86)/Graphviz2.38/bin'
        #prog  = os.path.join(path, prog)
        #prog += '.exe'
        self.prog = prog
        #return prog
在def create()函数中修改
if prog is None:
            prog = self.prog
        
        assert prog is not None
        #prog = self.set_prog('dot') #调用函数