Graphviz不会绘制决策树

Question

我目前对graphviz有问题。它不会在下面的代码中绘制决策树。

import pandas as pd
import graphviz 
df = pd.read_csv('https://github.com/QuantEcon/QuantEcon.lectures.code/raw/master/pandas/data/test_pwt.csv')
df[2:5]
from sklearn import datasets
from sklearn import tree
iris = datasets.load_iris()
iris
X, y = iris.data, iris.target
clf = tree.DecisionTreeClassifier()
clf = clf.fit(X, y)
print(clf)
dot_data = tree.export_graphviz(clf, out_file=None) 
graph = graphviz.Source(dot_data) 
graph.render("iris")
dot_data = tree.export_graphviz(clf, out_file=None, 
                      feature_names=iris.feature_names,  
                      class_names=iris.target_names,  
                      filled=True, rounded=True,  
                      special_characters=True)  
graph = graphviz.Source(dot_data)  
graph