Python编程从入门到实践 2016年7月第一版 (ing)

-------------------------------------------------------------------------------------------------------------------------------------始于2019年7月份

书籍阅读相关惑与得

英文版:在网盘中.

1. 《Python编程从入门到实践》第11章 测试代码使用书中推荐的Geany运行11.1.2节的代码结果与在pycharm中不一致.
   参考:关于PyCharm中Python测试不是run_testname 而是run_unittest_in_testname 的问题

2. Python编程从入门到实践》 第16.2.6节 btc_cllose_2017.py中,def draw_line函数.

y_list=[v for _,v in y]

相当于,

y_list=[]
for _,v in y:
    y_list.append(v)

ref:https://blog.csdn.net/dengpeiyi2012/article/details/90767789

3. 17.2.3节,python_repos.py出现如下报错:

ref:pygal制图“AttributeError: ‘NoneType’ object has no attribute ‘decode’

Traceback (most recent call last):
  File "C:/Users/vivi01.zhu/PycharmProjects/untitled2/python_repos.py", line 32, in 
    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'

从以下报错信息可以猜测出plot_dict中 "lbael"的description可能为null.经过检查,发现项目名为

 File "C:\Python27\lib\site-packages\pygal\util.py", line 233, in decorate
    metadata['label'])

解决方法1: 对repo_dict[‘description’]提前进行判断:

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)

 ———————————————— 
版权声明：本文为CSDN博主「waiwai3」的原创文章，遵循CC 4.0 by-sa版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/waiwai3/article/details/77847783

解决方法2: 对 description的值进行str. null的地方会显示成None.

 'label': str(repo_dict['description']),

完整代码如下:

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

url = 'https://api.github.com/search/repositories?q=language:python&sort=stars'
r = requests.get(url)
print("Status code:", r.status_code)

response_dict = r.json()
print("Total repositories: ", response_dict['total_count'])

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': str(repo_dict['description']),
        'xlink': repo_dict['html_url'],
    }
    plot_dicts.append(plot_dict)


# 可视化
my_style = LS('#003357', 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 = 20
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_repo.svg')

18.1.7 python manage.py migrate 命令出错

使用python版本与Django版本如下:

出错信息如下:

Traceback (most recent call last):
  File "manage.py", line 21, in 
    main()
  File "manage.py", line 17, in main
    execute_from_command_line(sys.argv)
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/core/management/__init__.py", line 363, in execute_from_command_line
    utility.execute()
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/core/management/__init__.py", line 337, in execute
    django.setup()
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/__init__.py", line 27, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/apps/registry.py", line 85, in populate
    app_config = AppConfig.create(entry)
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/apps/config.py", line 94, in create
    module = import_module(entry)
  File "/home/luoyu/anaconda3/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "", line 1006, in _gcd_import
  File "", line 983, in _find_and_load
  File "", line 967, in _find_and_load_unlocked
  File "", line 677, in _load_unlocked
  File "", line 728, in exec_module
  File "", line 219, in _call_with_frames_removed
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/contrib/admin/__init__.py", line 4, in 
    from django.contrib.admin.filters import (
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/contrib/admin/filters.py", line 10, in 
    from django.contrib.admin.options import IncorrectLookupParameters
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/contrib/admin/options.py", line 12, in 
    from django.contrib.admin import helpers, widgets
  File "/home/luoyu/PycharmProjects/learning_log/11_env/lib/python3.7/site-packages/django/contrib/admin/widgets.py", line 151
    '%s=%s' % (k, v) for k, v in params.items(),
    ^
SyntaxError: Generator expression must be parenthesized

分析得知道是Django与python版本兼容问题.(吐槽一下, 百度辣鸡,毛搜搜不到,stackoverflow 牛皮,O(∩_∩)O哈哈~)

.this is a known incompatibility between Django and Python 3.7. A fix has already been merged into Django 2.x branches and backported into 1.11 branch

solution: To solve this issue, simply update Django to at least version 1.11.17 (or 2.x) or you can downgrade Python to version 3.6.

 pip install django --upgrade

再次执行,

18 章 Django入门部分

由于书中用的Django版本过低,与本人采用的 (Python 3.7 Django 2.2.4)代码实现部分有区别.

18.3.1开始(代码参考: github链接( 待补充ing))

从入门到实践 Chapter18 第18章Django入门 映射URL 学习时的坑
关于Django Specifying a namespace in include() without providing an app_name

一些容易忽略的问题

1. 容易忽略的小问题
   1.1 有关model的使用(ref:模块的使用)
   我们可以用import 文件名的方式把它导入自己的新文件不过我们要注意创建的模块要符合命名规范，
   比如首字母不能是数字等.
   像如下图这种命令方式不可取.
   
   test2.py的内容如下:

def test():
    print("hell")

修改成如下名字后,导入自己写的模块成功运行.