1-Django - 报错集

目录

• centos7 pip安装uwsgi报错
• NameError: name 'Database' is not defined
• ImportError: urllib3 v2.0 only supports OpenSSL 1.1.1+, currently the 'ssl' module is compiled with 'OpenSSL 1.0.2k-fips 26 Jan 2017'. See: https://github.com/urllib3/urllib3/issues/2168
• UnicodeEncodeError: 'gbk' codec can't encode character '\ufffd' in position 1669: illegal multibyte sequence
• django.template.exceptions.TemplateSyntaxError: 'staticfiles' is not a registered tag library. Must
• django.core.exceptions.ImproperlyConfigured: Requested setting DEBUG, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.
• django.core.exceptions.ImproperlyConfigured: mysqlclient 1.3.13 or newer is required; you have 0.9.3.
• NameError: name '_mysql' is not defined
  • 解决方案1
  • 解决方案2
• SyntaxError: Generator expression must be parenthesized
• SyntaxError: Generator expression must be parenthesized (widgets.py, line 151)
• ValueError: The field admin.LogEntry.user was declared with a lazy reference to 'fault_reporting.userinfo', but app 'fault_reporting' isn't installed.
• RuntimeWarning: DateTimeField Message.date received a naive datetime .....
• TypeError: Object of type 'QuerySet' is not JSON serializable
• TypeError: Object of type Decimal is not JSON serializable
• AttributeError: Manager isn't available; 'auth.User' has been swapped for 'app01.UserInfo'
• Database returned an invalid datetime value. Are time zone definitions for your database installed?
• AttributeError: 'str' object has no attribute 'decode'
  • 情景1
  • 情景2
• UnicodeDecodeError: 'gbk' codec can't decode byte 0xa6 in position 9737: illegal multibyte sequence
• ValueError: source code string cannot contain null bytes
• "block" tag with name "device_list_class" appears more than once
• TypeError: isinstance() arg 2 must be a type or tuple of types
• app02.UserInfo.stu: (fields.E300) Field defines a relation with model 'Student', which is either not installed, or is abstract.
• binascii.Error: Invalid base64-encoded string: number of data characters (221) cannot be 1 more than a multiple of 4
• 'staticfiles' is not a registered tag library.Must be one of：
• django.db.utils.IntegrityError: NOT NULL constraint failed: django_admin_log.user_id
• AttributeError: 'AdminSite' object has no attribute '_registry'
• UnboundLocalError: local variable 'before_import_registry' referenced before assignment
• RuntimeError: 'cryptography' package is required for sha256_password or caching_sha2_password auth methods
• ModuleNotFoundError: No module named 'tencentcloud'

• 返回Django目录

centos7 pip安装uwsgi报错

原因之一就是缺少依赖：

yum install openssl-devel bzip2-devel expat-devel gdbm-devel readline-devel sqlite-devel psmisc libffi-devel  tk-devel pcre-devel

完事重新执行安装，如果再报错，就执行：

yum remve openssl-devel

反正就是各种尝试。

NameError: name 'Database' is not defined

centos7 + django3.2 + pymysql + mariadb

在服务器上执行python manage.py runserver时，发现报错：

(nb) [root@VM-0-12-centos day03]# python manage.py runserver 0.0.0.0:8002
Watching for file changes with StatReloader
Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/threading.py", line 1016, in _bootstrap_inner
    self.run()
  File "/usr/local/lib/python3.10/threading.py", line 953, in run
    self._target(*self._args, **self._kwargs)
  File "/envs/nb/lib/python3.10/site-packages/django/utils/autoreload.py", line 64, in wrapper
    fn(*args, **kwargs)
  File "/envs/nb/lib/python3.10/site-packages/django/core/management/commands/runserver.py", line 110, i
    autoreload.raise_last_exception()
  File "/envs/nb/lib/python3.10/site-packages/django/utils/autoreload.py", line 87, in raise_last_except
    raise _exception[1]
  File "/envs/nb/lib/python3.10/site-packages/django/core/management/__init__.py", line 375, in execute
    autoreload.check_errors(django.setup)()
  File "/envs/nb/lib/python3.10/site-packages/django/utils/autoreload.py", line 64, in wrapper
    fn(*args, **kwargs)
  File "/envs/nb/lib/python3.10/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/envs/nb/lib/python3.10/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/envs/nb/lib/python3.10/site-packages/django/apps/config.py", line 301, in import_models
    self.models_module = import_module(models_module_name)
  File "/usr/local/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/envs/nb/lib/python3.10/site-packages/django/contrib/auth/models.py", line 3, in <module>
    from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
  File "/envs/nb/lib/python3.10/site-packages/django/contrib/auth/base_user.py", line 48, in <module>
    class AbstractBaseUser(models.Model):
  File "/envs/nb/lib/python3.10/site-packages/django/db/models/base.py", line 122, in __new__
    new_class.add_to_class('_meta', Options(meta, app_label))
  File "/envs/nb/lib/python3.10/site-packages/django/db/models/base.py", line 326, in add_to_class
    value.contribute_to_class(cls, name)
  File "/envs/nb/lib/python3.10/site-packages/django/db/models/options.py", line 207, in contribute_to_c
    self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
  File "/envs/nb/lib/python3.10/site-packages/django/utils/connection.py", line 15, in __getattr__
    return getattr(self._connections[self._alias], item)
  File "/envs/nb/lib/python3.10/site-packages/django/utils/connection.py", line 62, in __getitem__
    conn = self.create_connection(alias)
  File "/envs/nb/lib/python3.10/site-packages/django/db/utils.py", line 204, in create_connection
    backend = load_backend(db['ENGINE'])
  File "/envs/nb/lib/python3.10/site-packages/django/db/utils.py", line 111, in load_backend
    return import_module('%s.base' % backend_name)
  File "/usr/local/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/envs/nb/lib/python3.10/site-packages/django/db/backends/mysql/base.py", line 35, in <module>
    version = Database.version_info
NameError: name 'Database' is not defined

最终的解决办法，就是修改其对应的源码，从报错中找到这个源码文件的位置：

File "/envs/nb/lib/python3.10/site-packages/django/db/backends/mysql/base.py", line 35, in <module>
    version = Database.version_info
NameError: name 'Database' is not defined

然后vim /envs/nb/lib/python3.10/site-packages/django/db/backends/mysql/base.py编辑这个文件，进行修改：

ImportError: urllib3 v2.0 only supports OpenSSL 1.1.1+, currently the 'ssl' module is compiled with 'OpenSSL 1.0.2k-fips 26 Jan 2017'. See: https://github.com/urllib3/urllib3/issues/2168

centos7 + django3.2 + uWSGI2.0.22 + urllib32.0

在项目部署时，执行uwsgi --ini uwsgi.ini命令之后，启动没问题，nginx也配上了，前端访问之后，uwsgi报错：

Traceback (most recent call last):
  File "/envs/book/lib/python3.9/site-packages/django/core/handlers/wsgi.py", line 133, in __call__
    response = self.get_response(request)
  File "/envs/book/lib/python3.9/site-packages/django/core/handlers/base.py", line 130, in get_response
    response = self._middleware_chain(request)
  File "/envs/book/lib/python3.9/site-packages/django/core/handlers/exception.py", line 49, in inner
    response = response_for_exception(request, exc)
  File "/envs/book/lib/python3.9/site-packages/django/core/handlers/exception.py", line 114, in response_for_exception
    response = handle_uncaught_exception(request, get_resolver(get_urlconf()), sys.exc_info())
  File "/envs/book/lib/python3.9/site-packages/django/core/handlers/exception.py", line 152, in handle_uncaught_exception
    callback = resolver.resolve_error_handler(500)
  File "/envs/book/lib/python3.9/site-packages/django/urls/resolvers.py", line 611, in resolve_error_handler
    callback = getattr(self.urlconf_module, 'handler%s' % view_type, None)
  File "/envs/book/lib/python3.9/site-packages/django/utils/functional.py", line 48, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/envs/book/lib/python3.9/site-packages/django/urls/resolvers.py", line 591, in urlconf_module
    return import_module(self.urlconf_name)
  File "/usr/local/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 855, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/data/www/book/./book/urls.py", line 20, in <module>
    path('api/reader/', include('apps.reader.urls')),
  File "/envs/book/lib/python3.9/site-packages/django/urls/conf.py", line 34, in include
    urlconf_module = import_module(urlconf_module)
  File "/usr/local/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 855, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/data/www/book/./apps/reader/urls.py", line 2, in <module>
    from apps.reader.views import account, basic, home, catalog, chapter, add_to_favorites
  File "/data/www/book/./apps/reader/views/home.py", line 1, in <module>
    import requests
  File "/envs/book/lib/python3.9/site-packages/requests/__init__.py", line 43, in <module>
    import urllib3
  File "/envs/book/lib/python3.9/site-packages/urllib3/__init__.py", line 41, in <module>
    raise ImportError(
ImportError: urllib3 v2.0 only supports OpenSSL 1.1.1+, currently the 'ssl' module is compiled with 'OpenSSL 1.0.2k-fips  26 Jan 2017'. See: https://github.com/urllib3/urllib3/issues/2168
[pid: 2154|app: 0|req: 2/2] 61.48.31.123 () {40 vars in 670 bytes} [Tue Aug 29 10:31:55 2023] GET /favicon.ico => generated 0 bytes in 11 msecs (HTTP/1.1 500) 0 headers in 0 bytes (0 switches on core 0)

参考stackoverflow上面的解决方案，一是升级openssl，二是降级urllib3的版本，我这里选择降级：

# 1. 先卸载urllib3
pip uninstall urllib3 -y

# 2. 再安装低版本的
pip install urllib3==1.26.6

完事之后，重新尝试就好了。
参考：https://stackoverflow.com/questions/76187256/importerror-urllib3-v2-0-only-supports-openssl-1-1-1-currently-the-ssl-modu

UnicodeEncodeError: 'gbk' codec can't encode character '\ufffd' in position 1669: illegal multibyte sequence

python3.10 + win10 + django4.2.3

在实现信号时，我打印了其中的kwargs形参，结果报错了：

截图中显示，第8行的print正常打印了，但到了第9行的打印就报错了，怀疑是print内部调用sys.stdout输出时，编码出了问题。

解决办法就是，在settings.py中，按照如下调整下sys.stdout输出时的编码。

# 解决方式1
# import sys
# sys.stdout.reconfigure(encoding='utf-8')

# 解决方式2，在项目运行时，添加下面的参数到环境变量
import os
os.environ['PYTHONIOENCODING'] = "utf-8"

django.template.exceptions.TemplateSyntaxError: 'staticfiles' is not a registered tag library. Must

django3.2/django4

这个问题有点玄乎，这是在自定义inclusion_tag时，报的错，开始我用的是django4，百度搜索的结果是在配置文件中添加如下一行：

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': []
        ,
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                # 'django.contrib.auth.context_processors.auth',
                # 'django.contrib.messages.context_processors.messages',
            ],
            # 就是下面这一行
            "libraries": {"staticfiles": "django.templatetags.static"},
        },
    },
]

后来我把django版本降到了django3.2，发现不用添加上面一行也行，所以怀疑是django版本的问题，但是换了台电脑，先用的django4，发现也不报错了....
所以，目前的解决办法是，只要你inclusion_tag各个步骤的配置没有问题，那么报这个错，就添加上这一行就行了。
参考:

• https://www.cnblogs.com/yizhipanghu/p/15346297.html
• https://www.oschina.net/question/3917555_2287629

django.core.exceptions.ImproperlyConfigured: Requested setting DEBUG, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.

win10 + django3.2

使用pycharm启动django项目，发现报错。注意下图中我的django服务配置，有问题。

解决办法，把settings相关的配置添加上就行了：

django.core.exceptions.ImproperlyConfigured: mysqlclient 1.3.13 or newer is required; you have 0.9.3.

执行数据迁移 python manage.py makemigrations 报错如下：

解决方案，注释掉 你的python解释器的Lib/site-packages/django/db/backends/mysql/base.py中的35和36行代码:

NameError: name '_mysql' is not defined

这个报错我遇到过两次，两次解决方案不同，所以先看解决方式1

解决方案1

centos7.5 + mysql5.7 + django3.2 + mysqlclient2.1.0 + python3.9.9

这是在Linux上使用python manage.py runserver 0.0.0.0:8000启动项目时，遇到的报错。
查了帖子，有三种解决方式：

1. 降低mysqlclient的版本，用1.x的版本，我没试。
2. 使用pymysql代替mysqlclient，这个方法可行。
3. 分析报错解决问题。

我的报错：

(venv) [root@cs mtb_server]# python manage.py runserver 0.0.0.0:8000
Watching for file changes with StatReloader
Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/opt/mtb/venv/lib/python3.9/site-packages/MySQLdb/__init__.py", line 18, in <module>
    from . import _mysql
ImportError: libmysqlclient.so.20: cannot open shared object file: No such file or directory

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/python39/lib/python3.9/threading.py", line 973, in _bootstrap_inner
    self.run()
  File "/opt/python39/lib/python3.9/threading.py", line 910, in run
    self._target(*self._args, **self._kwargs)
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/utils/autoreload.py", line 64, in wrapper
    fn(*args, **kwargs)
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/core/management/commands/runserver.py", line 110, in inner_run
    autoreload.raise_last_exception()
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/utils/autoreload.py", line 87, in raise_last_exception
    raise _exception[1]
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/core/management/__init__.py", line 375, in execute
    autoreload.check_errors(django.setup)()
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/utils/autoreload.py", line 64, in wrapper
    fn(*args, **kwargs)
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/apps/config.py", line 301, in import_models
    self.models_module = import_module(models_module_name)
  File "/opt/python39/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 850, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/opt/mtb/mtb_server/apps/base/models.py", line 4, in <module>
    class UserInfo(models.Model):
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/db/models/base.py", line 122, in __new__
    new_class.add_to_class('_meta', Options(meta, app_label))
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/db/models/base.py", line 326, in add_to_class
    value.contribute_to_class(cls, name)
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/db/models/options.py", line 207, in contribute_to_class
    self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/utils/connection.py", line 15, in __getattr__
    return getattr(self._connections[self._alias], item)
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/utils/connection.py", line 62, in __getitem__
    conn = self.create_connection(alias)
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/db/utils.py", line 204, in create_connection
    backend = load_backend(db['ENGINE'])
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/db/utils.py", line 111, in load_backend
    return import_module('%s.base' % backend_name)
  File "/opt/python39/lib/python3.9/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 850, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "/opt/mtb/venv/lib/python3.9/site-packages/django/db/backends/mysql/base.py", line 15, in <module>
    import MySQLdb as Database
  File "/opt/mtb/venv/lib/python3.9/site-packages/MySQLdb/__init__.py", line 24, in <module>
    version_info, _mysql.version_info, _mysql.__file__
NameError: name '_mysql' is not defined

很明显，我肯定百度了一下，从pypi上看到mysqlclient的解决办法：

sudo yum install python3-devel mysql-devel -y

链接：https://pypi.org/project/mysqlclient/
然后，再执行，还报错......
然后我继续分析报错内容：

Traceback (most recent call last):
  File "/opt/mtb/venv/lib/python3.9/site-packages/MySQLdb/__init__.py", line 18, in <module>
    from . import _mysql
ImportError: libmysqlclient.so.20: cannot open shared object file: No such file or directory

那就解决这个问题呗，从这个连接上找到了办法，链接：https://www.jianshu.com/p/4e22641c701c

(venv) [root@cs mtb_server]# find / -name "libmysqlclient.so.20"
/opt/software/mysql/lib/libmysqlclient.so.20
(venv) [root@cs mtb_server]# ln -s /opt/software/mysql/lib/libmysqlclient.so.20 /usr/lib64/libmysqlclient.so.20

查找libmysqlclient.so.20的位置，然后配置软链。
ok了，重新运行可以了。

(venv) [root@cs mtb_server]# python manage.py runserver 0.0.0.0:8000
Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).

You have 2 unapplied migration(s). Your project may not work properly until you apply the migrations for app(s): base.
Run 'python manage.py migrate' to apply them.
June 02, 2022 - 21:33:40
Django version 3.2, using settings 'mtb.settings'
Starting development server at http://0.0.0.0:8000/
Quit the server with CONTROL-C.

解决方案2

这个是我在mac m1芯片电脑上遇到的，当时的环境如下：

django4.2 + mysql5.7.31 + mysqlclient2.1.1 + pymsyql1.0.3 + mac m1芯片

在如上的开发环境下，在settings.py中，配置了关于链接MySQL的配置之后，运行项目，Django内部连接MySQL此时用的是mysqlclient模块，但很遗憾报错了如下的错误。

吐槽：mysqlclient安装之后，Django中无需特别的配置即可使用，真是非常方便，但是如果运行报错的话......经过几次解决踩坑经历，我个人推荐改用pymysql模块来代替mysqlclient，因为我试图解决过几次，发现得不偿失，还是pymysql香！

接下来的解决办法就是用的pymysql。

首先就是在项目同级目录下的__init__.py文件(或者说跟settings.py文件同级)中，添加如下两行代码。

一般就能直接运行了，如果你配置完能运行，就不用往下看了。

但很不幸，我的Django版本由于是4.x不知道是不是版本太高的问题，导致再次运行的时候，报了如下错误：django.core.exceptions.ImproperlyConfigured: mysqlclient 1.4.3 or newer is required; you have 1.0.3.

遇到报错只能解决了了啊，解决办法，就是在你解释器的安装目录中，修改源码，源码文件所在的位置在你的解释器安装目录中找Lib或者lib/python/中的site-packages/django/db/backends/mysql/base.py文件中的34-37行代码，注释掉即可。

按道理说，上面的源码注释掉，应该就是好了，如果你解决到这里，就能运行了，那就不需要往下看了。

但我继续运行项目，继续报错：django.db.utils.NotSupportedError: MySQL 8 or later is required (found 5.7.31).

好吧，继续找解决办法。

从一篇帖子上找到了解决方式：https://blog.bccn.net/静夜思/68210

那就找找到源码site-packages/django/db/backeds/base/base.py文件，直接ctrl+f搜索self.check_database_version_supported，然后把这一行注释掉。

然后，就解决了！！！

SyntaxError: Generator expression must be parenthesized

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：

[root@cs es_demo]# python37 manage.py runserver
Unhandled exception in thread started by <function check_errors.<locals>.wrapper at 0x7f220f0edae8>
Traceback (most recent call last):
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/autoreload.py", line 227, in wrapper
    fn(*args, **kwargs)
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/core/management/commands/runserver.py", line 117, in inner_run
    autoreload.raise_last_exception()
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/autoreload.py", line 250, in raise_last_exception
    six.reraise(*_exception)
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/utils/autoreload.py", line 227, in wrapper
    fn(*args, **kwargs)
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/__init__.py", line 27, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/apps/registry.py", line 85, in populate
    app_config = AppConfig.create(entry)
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/apps/config.py", line 94, in create
    module = import_module(entry)
  File "/usr/local/python/python37/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1006, in _gcd_import
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/contrib/admin/__init__.py", line 4, in <module>
    from django.contrib.admin.filters import (
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/contrib/admin/filters.py", line 10, in <module>
    from django.contrib.admin.options import IncorrectLookupParameters
  File "/usr/local/python/python37/lib/python3.7/site-packages/django/contrib/admin/options.py", line 12, in <module>
    from django.contrib.admin import helpers, widgets
  File "/usr/local/python/python37/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

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。

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。
see also：django1.11 启动错误：Generator expression must be parenthesized

SyntaxError: Generator expression must be parenthesized (widgets.py, line 151)

django1.11 + python3.9

同样是django项目运行时报错：

Exception ignored in thread started by: <function check_errors.<locals>.wrapper at 0x000001F56FCA28B0>
Traceback (most recent call last):
  File "D:\Python\lib\site-packages\django\utils\autoreload.py", line 227, in wrapper
    fn(*args, **kwargs)
  File "D:\Python\lib\site-packages\django\core\management\commands\runserver.py", line 117, in inner_run
    autoreload.raise_last_exception()
  File "D:\Python\lib\site-packages\django\utils\autoreload.py", line 250, in raise_last_exception
    six.reraise(*_exception)
  File "D:\Python\lib\site-packages\django\utils\six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "D:\Python\lib\site-packages\django\utils\autoreload.py", line 227, in wrapper
    fn(*args, **kwargs)
  File "D:\Python\lib\site-packages\django\__init__.py", line 27, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "D:\Python\lib\site-packages\django\apps\registry.py", line 85, in populate
    app_config = AppConfig.create(entry)
  File "D:\Python\lib\site-packages\django\apps\config.py", line 94, in create
    module = import_module(entry)
  File "D:\Python\lib\importlib\__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1030, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
  File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 790, in exec_module
  File "<frozen importlib._bootstrap>", line 228, in _call_with_frames_removed
  File "D:\Python\lib\site-packages\django\contrib\admin\__init__.py", line 4, in <module>
    from django.contrib.admin.filters import (
  File "D:\Python\lib\site-packages\django\contrib\admin\filters.py", line 10, in <module>
    from django.contrib.admin.options import IncorrectLookupParameters
  File "D:\Python\lib\site-packages\django\contrib\admin\options.py", line 12, in <module>
    from django.contrib.admin import helpers, widgets
SyntaxError: Generator expression must be parenthesized (widgets.py, line 151)

这个报错跟SyntaxError: Generator expression must be parenthesized报错说的是一回事儿，都是site-packages/django/contrib/admin/widgets.py文件的151行多了个逗号引起的：

解决办法也简单，删掉逗号就行了。

ValueError: The field admin.LogEntry.user was declared with a lazy reference to 'fault_reporting.userinfo', but app 'fault_reporting' isn't installed.

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.这类我们项目中不存在的app和模型类的错误。

而仔细观察，这个报错的app名字是我们之前某个项目中的app名字，而模型类则是那个app中定义的模型类，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目录下的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目录，删除除了__init__.py外的其他的文件。然后再次执行makemigrations即可。
see also：ValueError in Django when running the “python manage.py migrate” command

RuntimeWarning: DateTimeField Message.date received a naive datetime .....

当在module.py中定义DateTimeField类型的字段，在插入记录时：

import time
models.Message.objects.create(
     date=time.strftime("%Y-%m-%d %H:%M:%S", time.localtime())
)

虽然能够保存成功，但会发现一条警告：

C:\Python36\lib\site-packages\django\db\models\fields\__init__.py:1447: RuntimeWarning: DateTimeField Message.date received a naive datetime (2019-06-20 19:51:55) while time zone support is active.
  RuntimeWarning)

原因是，Django如果开启了Time Zone功能，则所有的存储和内部处理，甚至包括直接print显示全都是UTC的。只有通过模板进行表单输入渲染输出的时候，才会执行UTC本地时间的转换。所以我建议后台处理时间的时候，最好完全使用UTC，不要考虑本地时间的存在。而显示时间的时候，也避免手动转换，尽量使用Django模板系统代劳。

解决办法，可以在settings.py中将USE_TZ的默认True改为False。

USE_TZ = False

see also：django中使用时间帅选报RuntimeWarning: DateTimeField Coupon.valid_begin_date received a naive datetime (2018-08-16 20:51:40.135425) while time zone support is active.

TypeError: Object of type 'QuerySet' is not JSON serializable

Django1.11 + Python3.6 + win10

可能的原因

在ROM与ajax交互时，难免会遇到传递queryset对象，但是你会发现使用JsonResponse并不好用：

from django.shortcuts import render, HttpResponse
from django.http import JsonResponse
def ui_index(request):
    if request.method == 'POST':
        pk = request.POST.get('pk')
        result = ui_models.UiCase.objects.filter(case_vest_project=pk)
        # return HttpResponse({"case": result})
        return JsonResponse({"case": result})  # 依然不好使

就算使用JsonResponse({"case": result})依然不好使：

TypeError: Object of type 'QuerySet' is not JSON serializable

可能的解决办法

from django.core import serializers
def ui_index(request):
    if request.method == 'POST':
        pk = request.POST.get('pk')
        result = ui_models.UiCase.objects.filter(case_vest_project=pk)
        return JsonResponse({"case": serializers.serialize('json', result)})

这个时候，可以使用serializers来解决。然后前端的ajax正常接收即可，无需反序列化：

<script>
    $(".selected_project").on('click', 'li', function () {
        var pk = $(this).attr('pk');
        $.ajax({
            url: "{% url 'ui_index' %}",
            type: "POST",
            data: {'pk': pk},
            success: function (data) {
                console.log(typeof(data), data);
                if (data) {
                    $.each(data, function (index, item) {
                        console.log(item.case_name, item.pk, )
                    })
                }
            }
        })
    })
</script>

see also：【已解决】Object of type 'QuerySet' is not JSON serializable

TypeError: Object of type Decimal is not JSON serializable

这个跟上面的报错原理一样，json无法序列化Decimal类型的数据，所以，还要加判断，自己处理：

class CustomJsonEncoder(json.JSONEncoder):
    def default(self, field):
        if isinstance(field, date):
            return field.strftime('%Y-%m-%d')
        elif isinstance(field, datetime):
            return field.strftime('%Y-%m-%d %H:%M:%S')
        elif isinstance(field, decimal.Decimal):
            return float(field)
        else:
            return json.JSONEncoder.default(self, field)


class Books(View):

    def get(self, request):
        """ 查 """
        books = Book.objects.values('title', 'price')
        data_list = json.dumps(list(books), cls=CustomJsonEncoder)
        return HttpResponse(data_list, content_type="application/json")

我的表结构是这样的：

from django.db import models

class Book(models.Model):
    """ 书籍表 """
    title = models.CharField(max_length=32)
    price = models.DecimalField(max_digits=8, decimal_places=2)  # 999999.99

    def __str__(self):
        return self.title

AttributeError: Manager isn't available; 'auth.User' has been swapped for 'app01.UserInfo'

这个问题应该是在扩展django auth表时，出现的问题，如下示例：

# settings.py
AUTH_USER_MODEL = "app01.UserInfo"

# app01\models.py
from django.db import models
from django.contrib.auth.models import AbstractUser


class UserInfo(AbstractUser):  # 必须继承AbstractUser
    # 在django默认的user表的基础上添加字段
    phone = models.CharField(max_length=11, verbose_name='手机号')

# demo\test.py
import os
import django
from faker import Faker

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "demo.settings")  # demo：项目名称
django.setup()

from django.contrib.auth.models import auth, User

# from django.contrib.auth import get_user_model

# User = get_user_model()

fk = Faker(locale='zh_CN')


def foo():
    for i in range(3):
        User.objects.create_user(username=fk.name(), password='123', phone=fk.phone_number())
    # objs = auth.authenticate(username='王文', password='123')
    # print(objs)


if __name__ == '__main__':
    foo()

上面的代码运行就会报错：

解决办法就是，当扩展auth表后，你的user对象就不能像原来那样使用了，应该这么用：

import os
import django
from faker import Faker

os.environ.setdefault("DJANGO_SETTINGS_MODULE", "demo.settings")  # demo：项目名称
django.setup()

from django.contrib.auth.models import auth, User

# 导入它
from django.contrib.auth import get_user_model
User = get_user_model()  # 用get_user_model返回的User覆盖掉上面的User，其它代码不变

fk = Faker(locale='zh_CN')


def foo():
    for i in range(3):
        User.objects.create_user(username=fk.name(), password='123', phone=fk.phone_number())
    # objs = auth.authenticate(username='王文', password='123')
    # print(objs)


if __name__ == '__main__':
    foo()

Database returned an invalid datetime value. Are time zone definitions for your database installed?

时区问题：

解决，修改settings.py中的配置：

# 将
USE_TZ = True
# 改为：
USE_TZ = False

参考：

• https://stackoverflow.com/questions/40792628/django-mysql-database-returned-an-invalid-datetime-value
• https://www.codenong.com/cs109366948/

AttributeError: 'str' object has no attribute 'decode'

我在两种情况下遇到这个问题，而且也使用了两种方式进行解决，但后来测了下两种方式应该都可以。这里分别记录下。

情景1

Django2.2 + pymysql1.0.2 + mysql5.7

在Django2.2版本中，配置完毕MySQL的相关配置，重启服务时，发现报错：

Watching for file changes with StatReloader
Performing system checks...

System check identified no issues (0 silenced).
Exception in thread Thread-1:
Traceback (most recent call last):
  File "c:\python36\lib\threading.py", line 916, in _bootstrap_inner
    self.run()
  File "c:\python36\lib\threading.py", line 864, in run
    self._target(*self._args, **self._kwargs)
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\utils\autoreload.py", line 54, in wrapper
    fn(*args, **kwargs)
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\core\management\commands\runserver.py", line 120, in inner_run
    self.check_migrations()
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\core\management\base.py", line 453, in check_migrations
    executor = MigrationExecutor(connections[DEFAULT_DB_ALIAS])
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\migrations\executor.py", line 18, in __init__
    self.loader = MigrationLoader(self.connection)
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\migrations\loader.py", line 49, in __init__
    self.build_graph()
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\migrations\loader.py", line 212, in build_graph
    self.applied_migrations = recorder.applied_migrations()
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\migrations\recorder.py", line 73, in applied_migrations
    if self.has_table():
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\migrations\recorder.py", line 56, in has_table
    return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\base\base.py", line 256, in cursor
    return self._cursor()
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\base\base.py", line 233, in _cursor
    self.ensure_connection()
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\base\base.py", line 217, in ensure_connection
    self.connect()
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\base\base.py", line 197, in connect
    self.init_connection_state()
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\mysql\base.py", line 231, in init_connection_state
    if self.features.is_sql_auto_is_null_enabled:
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\utils\functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\mysql\features.py", line 82, in is_sql_auto_is_null_enabled
    cursor.execute('SELECT @@SQL_AUTO_IS_NULL')
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\utils.py", line 103, in execute
    sql = self.db.ops.last_executed_query(self.cursor, sql, params)
  File "D:\mydata\demo\all_env\django2.2\lib\site-packages\django\db\backends\mysql\operations.py", line 146, in last_executed_query
    query = query.decode(errors='replace')
AttributeError: 'str' object has no attribute 'decode'

经查，原因是Python安装目录下lib\site-packages\django\db\backends\mysql\operations.py这个文件中的last_executed_query方法中的源码写的有问题。

# 第140行开始
def last_executed_query(self, cursor, sql, params):
    # With MySQLdb, cursor objects have an (undocumented) "_executed"
    # attribute where the exact query sent to the database is saved.
    # See MySQLdb/cursors.py in the source distribution.
    query = getattr(cursor, '_executed', None)
    # 下面的if条件导致报错
    if query is not None:
        query = query.decode(errors='replace')
    return query

解决办法，在GitHub上，最新的Django版本源码中，https://github.com/django/django/blob/master/django/db/backends/mysql/operations.py`，第163-168行，该函数已经被修改为：

这就好办，我们照抄，将我们自己的源码也这么改下：

def last_executed_query(self, cursor, sql, params):
    # With MySQLdb, cursor objects have an (undocumented) "_executed"
    # attribute where the exact query sent to the database is saved.
    # See MySQLdb/cursors.py in the source distribution.
    query = getattr(cursor, '_executed', None)
    # 修改前的源码
    # if query is not None:
    #     query = query.decode(errors='replace')
    # return query
    # 修改后的源码
    from django.utils.encoding import force_str   # 只需要将这个导入，放到该模块的最上面即可
    return force_str(query, errors='replace')

然后重启Django就好了。
参考：Django2.2报错：：AttributeError: ''str'' object has no attribute ''decode'' | https://github.com/django/django/blob/master/django/db/backends/mysql/operations.py

情景2

python3.9.4 + django2.2 + pymysql1.0.2 + mysql5.7

这次是在Django中配置完了MySQL的相关配置之后，再做makemigrations时，遇到报错了：

xxdeMacBook-Pro:bookcms3 kanghua$ python3.9 manage.py makemigrations
Traceback (most recent call last):
  File "/Users/kanghua/PycharmProjects/python-note/study/bookcms3/manage.py", line 15, in <module>
    execute_from_command_line(sys.argv)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/core/management/__init__.py", line 381, in execute_from_command_line
    utility.execute()
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/core/management/__init__.py", line 375, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/core/management/base.py", line 323, in run_from_argv
    self.execute(*args, **cmd_options)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/core/management/base.py", line 364, in execute
    output = self.handle(*args, **options)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/core/management/base.py", line 83, in wrapped
    res = handle_func(*args, **kwargs)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/core/management/commands/makemigrations.py", line 101, in handle
    loader.check_consistent_history(connection)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/migrations/loader.py", line 283, in check_consistent_history
    applied = recorder.applied_migrations()
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/migrations/recorder.py", line 73, in applied_migrations
    if self.has_table():
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/migrations/recorder.py", line 56, in has_table
    return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/base/base.py", line 256, in cursor
    return self._cursor()
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/base/base.py", line 233, in _cursor
    self.ensure_connection()
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/base/base.py", line 217, in ensure_connection
    self.connect()
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/base/base.py", line 197, in connect
    self.init_connection_state()
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/mysql/base.py", line 231, in init_connection_state
    if self.features.is_sql_auto_is_null_enabled:
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/utils/functional.py", line 80, in __get__
    res = instance.__dict__[self.name] = self.func(instance)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/mysql/features.py", line 82, in is_sql_auto_is_null_enabled
    cursor.execute('SELECT @@SQL_AUTO_IS_NULL')
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/utils.py", line 103, in execute
    sql = self.db.ops.last_executed_query(self.cursor, sql, params)
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/django/db/backends/mysql/operations.py", line 146, in last_executed_query
    query = query.decode(errors='replace')
AttributeError: 'str' object has no attribute 'decode'

然后，搞笑的是，我忘记了曾经解决过这个问题了，就又去百度搜的......
先说解决方案，按照报错的最后一行提示lib/python3.9/site-packages/django/db/backends/mysql/operations.py这个源码文件的146行报错了，那就改吧：

完事之后，重新做数据库迁移，应该就可以了：

xxdeMacBook-Pro:bookcms3 kanghua$ python3.9 manage.py makemigrations
Migrations for 'book':
  book/migrations/0001_initial.py
    - Create model Author
    - Create model Publish
    - Create model Book

感觉要比情景一中的解决要简单啊！最后，没啥说的，用哪种解决方式都行，只要能解决问题的方案就是好方案！
参考：Django+MySQL+python报错：AttributeError: ‘str‘ object has no attribute ‘decode‘

UnicodeDecodeError: 'gbk' codec can't decode byte 0xa6 in position 9737: illegal multibyte sequence

Django2.2 + Python3.6.8

在Django2.2和django3版本中，如果访问页面，后台报：

UnicodeDecodeError: 'gbk' codec can't decode byte 0xa6 in position 9737: illegal multibyte sequence

这种情况是源码存在读文件编码没有设置的问题，根据报错的历史回溯发现，在你的*lib\site-packages\django\views\debug.py这个文件的331行有问题：
修改前：

修改后：

现在就可以正常的访问了。
参考：https://blog.csdn.net/qq_37232731/article/details/89684409

ValueError: source code string cannot contain null bytes

django项目中，报这个错误时，第一怀疑对象是各个py文件的编码格式不一样导致的，请检查并将所有文件的编码保持一致，推荐使用utf-8编码。
如果你用的是pycharm，File→Settings→Editor→File Encodings，修改Project Encoding和Properties Files都为UTF-8编码格式就完了。

"block" tag with name "device_list_class" appears more than once

这个报错指的是，在一个模板中(一个html页面中)不能同时定义多个同名的block块。

来自官网的解释：Finally, note that you can’t define multiple block tags with the same name in the same template. This limitation exists because a block tag works in “both” directions. That is, a block tag doesn’t just provide a hole to fill – it also defines the content that fills the hole in the parent. If there were two similarly-named block tags in a template, that template’s parent wouldn’t know which one of the blocks’ content to use.

TypeError: isinstance() arg 2 must be a type or tuple of types

win10 + django3.2

注意，这个错误本身是个外键字段to后的模型类需不需要带引号的问题，但是报错却不太一样。
当前这个报错是我扩展auth_user表时，做外键关联时，发生的问题。如果不是扩展auth_user表，则是另外的报错参考本篇app02.UserInfo.stu: (fields.E300) Field defines a relation with model 'Student', which is either not installed, or is abstract. app02.UserInfo.stu: (fields.E307) The field app02.UserInfo.stu was declared with a lazy reference to 'app02.student', but app 'app02' do esn't provide model 'student'.部分。
先来看扩展auth_user表时，遇到的报错，也就是TypeError: isinstance() arg 2 must be a type or tuple of types报错。
我们说，绑定外键，你可以：

from django.db import models
from django.contrib.auth.models import AbstractUser  # 别忘了导入


class UserDetail(models.Model):
    phone = models.CharField(max_length=11, verbose_name='手机号', default='')


class UserInfo(AbstractUser):  # 必须继承这个AbstractUser类
    # to后面的类，可以带引号或者不带引号
    # detail = models.OneToOneField(to="UserDetail", on_delete=models.CASCADE)
    detail = models.OneToOneField(to=UserDetail, on_delete=models.CASCADE)

    def __str__(self):
        return self.username

这样，你做数据库迁移的时候，不报错，但是，注意！！！这是有前提的，这要外键关联的表也在同一个models中。
如果你外键关联表再别的models中，你就不能使用带引号的形式了：

from django.db import models
from django.contrib.auth.models import AbstractUser  # 别忘了导入
from app02.models import Student  # 另一个app中的Student模型类


class UserDetail(models.Model):
    phone = models.CharField(max_length=11, verbose_name='手机号', default='')


class UserInfo(AbstractUser):  # 必须继承这个AbstractUser类
    # 外键关联模型类，在同一个models中，to后面的类，可以带引号或者不带引号
    # 带引号的话，默认在当前models中找，我们的UserDetail正好符合条件，所以没问题
    detail = models.OneToOneField(to=UserDetail, on_delete=models.CASCADE)

    # 注意，如果外键关联的模型类，在另一个models中，如下面的stu字段，关联的模型类在另一个app的models中
    # to后面的模型类，带引号的话，数据库迁移时，就会报错：TypeError: isinstance() arg 2 must be a type or tuple of types
    # 那就不能带引号了
    # stu = models.OneToOneField(to='Student', on_delete=models.CASCADE)  # 数据库迁移报错
    stu = models.OneToOneField(to=Student, on_delete=models.CASCADE)  # 数据库迁移不报错

    def __str__(self):
        return self.username

参考：https://blog.csdn.net/weixin_30639719/article/details/99091219

app02.UserInfo.stu: (fields.E300) Field defines a relation with model 'Student', which is either not installed, or is abstract.

win10 + django3.2

这个报错跟本篇TypeError: isinstance() arg 2 must be a type or tuple of types这个报错，其实说的是一个问题，报本小节这个错误，就是普通的外键关联模型类时，指定to后面的模型类加了引号，导致的。
首先app01.models.py：

from django.db import models

class Student(models.Model):
    name = models.CharField(max_length=32)

然后app02.models中引入了app01的student模型类，然后......由于引号引发的报错：

from django.db import models
from app01.models import Student


class UserDetail(models.Model):
    phone = models.CharField(max_length=11, verbose_name='手机号', default='')


class UserInfo(models.Model):
    # 外键关联模型类，在同一个models中，to后面的类，可以带引号或者不带引号
    # 带引号的话，默认在当前models中找，我们的UserDetail正好符合条件，所以没问题
    detail = models.OneToOneField(to=UserDetail, on_delete=models.CASCADE)

    # 注意，如果外键关联的模型类，在另一个models中，如下面的stu字段，关联的模型类在另一个app的models中
    # to后面的模型类，带引号的话，数据库迁移时，就会报错
    # 那就不能带引号了
    # stu = models.OneToOneField(to='Student', on_delete=models.CASCADE)  # 数据库迁移报错
    stu = models.OneToOneField(to=Student, on_delete=models.CASCADE)  # 数据库迁移不报错

加引号报错：

(base) D:\downloads\demo>python manage.py makemigrations
SystemCheckError: System check identified some issues:

ERRORS:
app02.UserInfo.stu: (fields.E300) Field defines a relation with model 'Student', which is either not installed, or is abstract.
app02.UserInfo.stu: (fields.E307) The field app02.UserInfo.stu was declared with a lazy reference to 'app02.student', but app 'app02' do
esn't provide model 'student'.

binascii.Error: Invalid base64-encoded string: number of data characters (221) cannot be 1 more than a multiple of 4

django1.11

这个报错挺奇妙的，访问admin页面报错：

Internal Server Error: /admin/
Traceback (most recent call last):
  File "D:\env\env2\lib\site-packages\django\contrib\sessions\backends\base.py", line 202, in _get_session
    return self._session_cache
AttributeError: 'SessionStore' object has no attribute '_session_cache'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:\env\env2\lib\site-packages\django\core\handlers\exception.py", line 41, in inner
    response = get_response(request)
  File "D:\env\env2\lib\site-packages\django\core\handlers\base.py", line 187, in _get_response
    response = self.process_exception_by_middleware(e, request)
  File "D:\env\env2\lib\site-packages\django\core\handlers\base.py", line 185, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "D:\env\env2\lib\site-packages\django\contrib\admin\sites.py", line 242, in wrapper
    return self.admin_view(view, cacheable)(*args, **kwargs)
  File "D:\env\env2\lib\site-packages\django\utils\decorators.py", line 149, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "D:\env\env2\lib\site-packages\django\views\decorators\cache.py", line 57, in _wrapped_view_func
    response = view_func(request, *args, **kwargs)
  File "D:\env\env2\lib\site-packages\django\contrib\admin\sites.py", line 213, in inner
    if not self.has_permission(request):
  File "D:\env\env2\lib\site-packages\django\contrib\admin\sites.py", line 187, in has_permission
    return request.user.is_active and request.user.is_staff
  File "D:\env\env2\lib\site-packages\django\utils\functional.py", line 238, in inner
    self._setup()
  File "D:\env\env2\lib\site-packages\django\utils\functional.py", line 385, in _setup
    self._wrapped = self._setupfunc()
  File "D:\env\env2\lib\site-packages\django\contrib\auth\middleware.py", line 24, in <lambda>
    request.user = SimpleLazyObject(lambda: get_user(request))
  File "D:\env\env2\lib\site-packages\django\contrib\auth\middleware.py", line 12, in get_user
    request._cached_user = auth.get_user(request)
  File "D:\env\env2\lib\site-packages\django\contrib\auth\__init__.py", line 210, in get_user
    user_id = _get_user_session_key(request)
  File "D:\env\env2\lib\site-packages\django\contrib\auth\__init__.py", line 61, in _get_user_session_key
    return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
  File "D:\env\env2\lib\site-packages\django\contrib\sessions\backends\base.py", line 57, in __getitem__
    return self._session[key]
  File "D:\env\env2\lib\site-packages\django\contrib\sessions\backends\base.py", line 207, in _get_session
    self._session_cache = self.load()
  File "D:\env\env2\lib\site-packages\django\contrib\sessions\backends\db.py", line 37, in load
    return self.decode(s.session_data)
  File "D:\env\env2\lib\site-packages\django\contrib\sessions\backends\base.py", line 103, in decode
    encoded_data = base64.b64decode(force_bytes(session_data))
  File "c:\users\26217\appdata\local\programs\python\python39\lib\base64.py", line 87, in b64decode
    return binascii.a2b_base64(s)
binascii.Error: Invalid base64-encoded string: number of data characters (221) cannot be 1 more than a multiple of 4
[05/May/2022 15:19:44] "GET /admin/ HTTP/1.1" 500 134139
[05/May/2022 15:21:00] "GET /admin/ HTTP/1.1" 302 0
[05/May/2022 15:21:00] "GET /admin/login/?next=/admin/ HTTP/1.1" 200 1650

通过观察报错内容发现两个重要的报错信息：

AttributeError: 'SessionStore' object has no attribute '_session_cache'

binascii.Error: Invalid base64-encoded string: number of data characters (221) cannot be 1 more than a multiple of 4

发现报错跟session有关，那么解决办法首先尝试：

1. 重新做数据库迁移命令，未解决！
2. 检查django内置session表，是否有内容，如果的话选择手动清空session表记录，然后再重新访问发现就好了。

参考：https://stackoverflow.com/questions/54722170/django-sessionstore-object-has-no-attribute-session-cache

---

that's all, see also:

Pycharm设置默认UTF8编码格式

'staticfiles' is not a registered tag library.Must be one of：

django3.2

这个报错应该是使用django3运行django1版本开发的项目，报错截图：

而django3的官档对此作了说明，移除了staticfiles

官档链接：https://docs.djangoproject.com/en/dev/releases/3.0/#features-removed-in-3-0

那解决办法也好办，就是将{% load staticfiels %}改为{% load static %}。
或者参考StackOverflow：https://stackoverflow.com/questions/55929472/django-templatesyntaxerror-staticfiles-is-not-a-registered-tag-library，配置settings。

django.db.utils.IntegrityError: NOT NULL constraint failed: django_admin_log.user_id

win10 + python3.9 + django1.11 + sqlite3

法1
数据库执行makemigrations成功，执行migrate报错django.db.utils.IntegrityError: NOT NULL constraint failed: django_admin_log.user_id，这是外键约束的错误。
想了想这是从别的地方拿来的项目，数据都有，就是拿过来之后，执行数据库迁移报错了。
解决办法，就是找到sLib\site-packages\django\contrib\admin\migrations目录，将其内的000开头的py文件都删掉，然后重新执行数据库迁移命令就可以了。

法2
方法1要是不灵，那肯定是你模型类的外键定义的问题了，即外键字段需要传值，你添加数据的时候没有传，导致的报错。
但就是不想传值咋办？好办，添加一个null=True属性，然后重新执行数据库迁移那两条命令，应该就好了。
让外键字段可以为空。

AttributeError: 'AdminSite' object has no attribute '_registry'

django1.11

这是个非常神奇的错误，我原本用的是django1.11版本，然后就创建好项目之后，启动报这个错，怎么都没排出来.....
原谅我太菜！！！
后来，我就把django1.11卸载了！换了django1.11.29版本(django1.x的最后一个版本了)。
然后就好了。

UnboundLocalError: local variable 'before_import_registry' referenced before assignment

django1.11

这是个非常神奇的错误，跟解决AttributeError: 'AdminSite' object has no attribute '_registry'报错时遇到的，我原本用的是django1.11版本，然后就创建好项目之后，启动报这个错，怎么都没排出来.....
原谅我太菜！！！
后来，我就把django1.11卸载了！换了django1.11.29版本(django1.x的最后一个版本了)。
然后就好了。

RuntimeError: 'cryptography' package is required for sha256_password or caching_sha2_password auth methods

django3.2 + mysql8.0

项目中配置了mysql之后，运行报错：

RuntimeError: 'cryptography' package is required for sha256_password or caching_sha2_password auth methods

解决办法就是，下载cryptography模块：

pip install cryptography

ModuleNotFoundError: No module named 'tencentcloud'

报这个错，一般是在使用腾讯云短信时忘了下载对应的模块了，解决办法就是下载这个模块就好了：

pip install --upgrade tencentcloud-sdk-python