pygal制图“AttributeError: 'NoneType' object has no attribute 'decode'”

最近在看<Python变成：从入门到实践>书中的17章 使用Web Api

17.2.3 根据数据绘图

# coding=utf-8import requestsimport pygalfrom pygal.style import LightColorizedStyle as LCS, LightenStyle as LS# 执行API调用并存储响应URL = 'https://api.github.com/search/repositories?q=language:python&sort=star'r = requests.get(URL)print("Status code:", r.status_code)# 将API响应存储在一个变量中response_dict = r.json()print("Total repositories:", response_dict['total_count'])# 研究有关仓库的信息repo_dicts = response_dict['items']print "Number of items:",len(repo_dicts)names,plot_dicts=[],[]for repo_dict in repo_dicts:    names.append(repo_dict['name'])    if repo_dict['description']:        plot_dict={'value':repo_dict['stargazers_count'],                   'label':repo_dict['description'],                   'xlink':repo_dict['html_url']                   }        plot_dicts.append(plot_dict)    else:        plot_dict={'value':repo_dict['stargazers_count'],                   'label':'ABC',                   'xlink':repo_dict['html_url']}        plot_dicts.append(plot_dict)# 可视化my_style = LS('#333366', base_style=LCS)chart = pygal.Bar(style=my_style, x_label_rotation=45, show_legend=False)chart.title = 'Most-Starred Python Projects on GitHub'chart.x_labels = nameschart.add('', plot_dicts)print plot_dictschart.render_to_file('python_repos.svg')

上面的代码和书中有些不同，主要是

for repo_dict in repo_dicts:    names.append(repo_dict['name'])    if repo_dict['description']:        plot_dict={'value':repo_dict['stargazers_count'],                   'label':repo_dict['description'],                   'xlink':repo_dict['html_url']                   }        plot_dicts.append(plot_dict)    else:        plot_dict={'value':repo_dict['stargazers_count'],                   'label':'ABC',                   'xlink':repo_dict['html_url']}        plot_dicts.append(plot_dict)

为什么加上这段？

按书上的写法，出现如下报错

Traceback (most recent call last):  File "C:/Users/vivi01.zhu/PycharmProjects/untitled2/python_repos.py", line 32, in <module>    chart.render_to_file('python_repos.svg')  File "C:\Python27\lib\site-packages\pygal\graph\public.py", line 114, in render_to_file    f.write(self.render(is_unicode=True, **kwargs))  File "C:\Python27\lib\site-packages\pygal\graph\public.py", line 52, in render    self.setup(**kwargs)  File "C:\Python27\lib\site-packages\pygal\graph\base.py", line 217, in setup    self._draw()  File "C:\Python27\lib\site-packages\pygal\graph\graph.py", line 933, in _draw    self._plot()  File "C:\Python27\lib\site-packages\pygal\graph\bar.py", line 146, in _plot    self.bar(serie)  File "C:\Python27\lib\site-packages\pygal\graph\bar.py", line 116, in bar    metadata)  File "C:\Python27\lib\site-packages\pygal\util.py", line 233, in decorate    metadata['label'])  File "C:\Python27\lib\site-packages\pygal\_compat.py", line 61, in to_unicode    return string.decode('utf-8')AttributeError: 'NoneType' object has no attribute 'decode'

需要显示在图上的plot_dicts可以打印出来，且正常

猜测是因为其中有个参数(repo_dict的description)为none，无属性，对此参数加上是否为none的if--else判断，运行通过，bingo~

('Status code:', 200)('Total repositories:', 1923446)Number of items: 30[{'xlink': u'https://github.com/vinta/awesome-python', 'value': 38175, 'label': u'A curated list of awesome Python frameworks, libraries, software and resources'}.................{'xlink': u'https://github.com/drduh/macOS-Security-and-Privacy-Guide', 'value': 11824, 'label': u'A practical guide to securing macOS.'}]Process finished with exit code 0