django2.0发行文档说，django2.0最后一个支持的是python3.4+... 所以，还在用python2.7的同学只能手动指定版本下载了 pip2 install django==1.8.17 或 pip2 install django==1.10 摘自：https://docs.djangoproject.com/en/2.0/releases/2.0/
''' 在新创建的Django项目中执行makemigrations时，遇到： ValueError: The field admin.LogEntry.user was declared with a lazy reference to 'fault_reporting.userinfo', but app 'fault_reporting' isn't installed. 这类app并没有安装的错误 而仔细观察，这个报错的app名字是我们之前项目中的app名字，但现在却在我们当前的项目中报错了。究其原因，则是因为之前的项目中的app缓存被存在了Django的模块内的"某些地方" 而我们当在新的项目中用到"某些地方"的功能时，执行了之前的缓存内容，从而引发错误 而普通的解决办法，就是删除当前项目中的.idea文件和__pycache__文件，然后就是删除migrations文件下的00开头的py文件都解决不了。甚至是卸载Django重新安装————都没用！ 因为我们并没有删除Django模块中"某些地方"的缓存文件(pip uninstall Django都清不了这些缓存文件)。so，我们要手动去删除这这个"某个地方"的缓存文件 打开你的解释器下的Lib\site-packages\django\contrib\admin\migrations 删除除了__init__.py外的其他的文件 然后再次运行makemigrations即可 see also：https://stackoverflow.com/questions/40222268/valueerror-in-django-when-running-the-python-manage-py-migrate-command '''
from django.db import models class UserInfo(models.Model): user = models.CharField(max_length=32) pwd = models.CharField(max_length=32) class Token(models.Model): user = models.OneToOneField(UserInfo,on_delete=None) token = models.CharField(max_length=64) # 关键字on_delete=None # 2.0版本在源码中取消了on_delete=None，需要手动传递， class OneToOneField(ForeignKey): def __init__(self, to, on_delete, to_field=None, **kwargs): # 源码中取消默认值 kwargs['unique'] = True super().__init__(to, on_delete, to_field=to_field, **kwargs) # 而在django1.11.5和1.8.17版本中，都是有默值的 def __init__(self, to, on_delete=None, to_field=None, **kwargs):
1 启动报错：SyntaxError: Generator expression must be parenthesized，有时候，在使用命令python manager.py runserver时，会发先启动失败，报错日志如下： 2 [root@cs es_demo]# python37 manage.py runserver 3 Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x7f220f0edae8> 4 Traceback (most recent call last): 5 File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/autoreload.py", line 227, in wrapper 6 fn(*args, **kwargs) 7 File "/usr/local/python/python37/lib/python3.7/site-packages/django/core/management/commands/runserver.py", line 117, in inner_run 8 autoreload.raise_last_exception() 9 File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/autoreload.py", line 250, in raise_last_exception 10 six.reraise(*_exception) 11 File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/six.py", line 685, in reraise 12 raise value.with_traceback(tb) 13 File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/autoreload.py", line 227, in wrapper 14 fn(*args, **kwargs) 15 File "/usr/local/python/python37/lib/python3.7/site-packages/django/__init__.py", line 27, in setup 16 apps.populate(settings.INSTALLED_APPS) 17 File "/usr/local/python/python37/lib/python3.7/site-packages/django/apps/registry.py", line 85, in populate 18 app_config = AppConfig.create(entry) 19 File "/usr/local/python/python37/lib/python3.7/site-packages/django/apps/config.py", line 94, in create 20 module = import_module(entry) 21 File "/usr/local/python/python37/lib/python3.7/importlib/__init__.py", line 127, in import_module 22 return _bootstrap._gcd_import(name[level:], package, level) 23 File "<frozen importlib._bootstrap>", line 1006, in _gcd_import 24 File "<frozen importlib._bootstrap>", line 983, in _find_and_load 25 File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked 26 File "<frozen importlib._bootstrap>", line 677, in _load_unlocked 27 File "<frozen importlib._bootstrap_external>", line 728, in exec_module 28 File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed 29 File "/usr/local/python/python37/lib/python3.7/site-packages/django/contrib/admin/__init__.py", line 4, in <module> 30 from django.contrib.admin.filters import ( 31 File "/usr/local/python/python37/lib/python3.7/site-packages/django/contrib/admin/filters.py", line 10, in <module> 32 from django.contrib.admin.options import IncorrectLookupParameters 33 File "/usr/local/python/python37/lib/python3.7/site-packages/django/contrib/admin/options.py", line 12, in <module> 34 from django.contrib.admin import helpers, widgets 35 File "/usr/local/python/python37/lib/python3.7/site-packages/django/contrib/admin/widgets.py", line 151 36 '%s=%s' % (k, v) for k, v in params.items(), 37 ^ 38 SyntaxError: Generator expression must be parenthesized 39 40 可以发现最后一行提示说是语法错误，说是生成器表达式有问题，那具体的报错行内容是'%s=%s' % (k, v) for k, v in params.items(),，可以看到，最后一个标点符号很有意思，我们找到源码文件对应的行，把这个标点符号去掉即可。 41 ps：如果是pycharm中修改的话，由于这个文件是源码，还要注意提示框中选择I want to edit this file anyway。
欢迎斧正，that's all
