AttributeError:“列表"对象没有属性"create_png" [英] AttributeError: 'list' object has no attribute 'create_png'

问题描述

这将数据分类为决策树.决策树已创建，但我无法查看决策树.

This classifies the data as a decision tree. The decision tree is created but I am not able to view the decision tree.

import numpy as np
from sklearn import linear_model, datasets, tree
import matplotlib.pyplot as plt
iris = datasets.load_iris()
f = open('decision_tree_data.txt')
x_train = []
y_train = []
for line in f:
    line = np.asarray(line.split(),dtype = np.float32)
    x_train.append(line[:-1])
    y_train.append(line[:-1])
x_train = np.asmatrix(x_train)
y_train = np.asmatrix(y_train)
model = tree.DecisionTreeClassifier()
model.fit(x_train,y_train)
from sklearn.externals.six import StringIO
import pydot
from IPython.display import Image
dot_data = StringIO()
tree.export_graphviz(model, out_file=dot_data,  
                     feature_names=iris.feature_names,  
                     class_names=iris.target_names,  
                     filled=True, rounded=True,  
                     special_characters=True)  
graph = pydot.graph_from_dot_data(dot_data.getvalue()) 
Image(graph.create_png())

推荐答案

函数pydot.graph_from_dot_data 返回 a list 在 (与pydot的早期版本相比).

The function pydot.graph_from_dot_data returns a list in pydot >= 1.2.0 (in contrast to earlier versions of pydot).

原因是使输出均匀化，过去如果返回两个图，则为list，但是如果返回单个图则为list.这样的分支是用户代码错误的常见来源(简单优于复杂[[a href ="https://www.python.org/dev/peps/pep-0020/" rel ="nofollow noreferrer"> PEP 20 ]).

The reason was to homogenize the output, which in the past was a list if two graphs were returned, but a graph if a single graph was returned. Such branching is a common source of errors in user code (simple is better than complex [PEP 20]).

更改适用于调用函数dot_parser.parse_dot_data的所有函数，该函数现在返回

The change applies to all functions that call the function dot_parser.parse_dot_data, which now returns a list in all cases.

要解决该错误，您需要解压缩期望的单个图:

To address the error, you need to unpack the single graph that you expect:

(graph,) = pydot.graph_from_dot_data(dot_data.getvalue())

此语句还断言将返回单个图形.因此，如果这种假设不成立，并且返回了更多的图形，则解压缩将捕获该图形.相反，graph = (...)[0]不会.

This statement also asserts that a single graph is returned. So if this assumption doesn't hold, and more graphs are returned, this unpacking will catch it. In contrast, graph = (...)[0] won't.

相关的pydot问题:

• https://github.com/erocarrera/pydot/issues/149
• https://github.com/erocarrera/pydot/issues/159

• https://github.com/erocarrera/pydot/issues/149
• https://github.com/erocarrera/pydot/issues/159

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