python - chart.render_to_file ('python_repos.svg' )AttributeError : 'NoneType' object has no attribute 'decode'

Question

我正在通过这本书学习 Python:“Python 速成类(class):基于项目的动手编程入门”。在“Working with APIs”一书的第 17 章中，我按照书上的说明进行操作，但出现错误。我不知道错误是什么意思。这是否意味着站点包有问题？如何解决？

import requests
import pygal
from pygal.style import LightColorizedStyle as LCS, LightenStyle as LS

# Make an API call, and store the response.
url = 'https://api.github.com/search/repositories?q=language:python&sort=stars'
r = requests.get(url)
print("Status code:", r.status_code)

# Store API response in a variable.
response_dict = r.json()
print("Total repositories:", response_dict['total_count'])

# Explore information about the repositories.
repo_dicts = response_dict['items']

names, plot_dicts = [], []
for repo_dict in repo_dicts:
    names.append(repo_dict['name'])

    plot_dict = {
        'value': repo_dict['stargazers_count'],
        'label': repo_dict['description'],
        }
    plot_dicts.append(plot_dict)

# Make visualization.
my_style = LS('#333366', base_style=LCS)

my_config = pygal.Config()
my_config.x_label_rotation = 45
my_config.show_legend = False
my_config.title_font_size = 24
my_config.label_font_size = 14
my_config.major_label_font_size = 18
my_config.truncate_label = 15
my_config.show_y_guides = False
my_config.width = 1000

chart = pygal.Bar(my_config, style=my_style)
chart.title = 'Most-Starred Python Projects on GitHub'
chart.x_labels = names

chart.add('', plot_dicts)
chart.render_to_file('python_repos.svg')

错误如下

Status code: 200
Total repositories: 2198954
Traceback (most recent call last):
  File "2018-07-13-1.py", line 45, in <module>
    chart.render_to_file('python_repos.svg')
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\graph\public.py", line 114, in render_to_file
    f.write(self.render(is_unicode=True, **kwargs))
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\graph\public.py", line 52, in render
    self.setup(**kwargs)
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\graph\base.py", line 217, in setup
    self._draw()
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\graph\graph.py", line 933, in _draw
    self._plot()
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\graph\bar.py", line 146, in _plot
    self.bar(serie)
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\graph\bar.py", line 116, in bar
    metadata)
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\util.py", line 233, in decorate
    metadata['label'])
  File "C:\Users\Administrator\AppData\Roaming\Python\Python35\site-packages\pygal\_compat.py", line 61, in to_unicode
    return string.decode('utf-8')
AttributeError: 'NoneType' object has no attribute 'decode'

Answer 1

错误是由您在图表上设置的标签之一 None 引起的，它是 Python's special built-in constants 之一。 .当 pygal 开始渲染图表时，它希望标签是一个字符串并调用 decode 函数。此函数在 None 对象上不存在，因此会引发错误。

查看 Github 存储库的名称和描述(您分别将其设置为 x 标签和数据标签)，我们可以看到其中一个存储库的描述是 None。我不会说这本书中的代码有什么特别的错误，只是运气不好，目前最受关注的 Python 存储库没有任何描述。

我们可以通过检查 for 循环中的 None 值来解决这个问题:

for repo_dict in repo_dicts:

    if repo_dict['name'] is None:
        names.append('')  # Empty string.
    else:
        names.append(repo_dict['name'])

    plot_dict = {'value': repo_dict['stargazers_count']}
    if repo_dict['description'] is not None:
        plot_dict['label'] = repo_dict['description']

    plot_dicts.append(plot_dict)

在第一部分中，我们添加了一个空字符串来代替任何 None 值(因为当您设置 x 标签时，您将需要一些东西)。

在第二部分中，我们创建了仅包含值的字典，然后仅当描述不是 None 时才将描述添加为标签。