编辑于2020年8月18日

Question

我在本地计算机上有一个正在运行的Django博客，其中包含sqlite3 db。我想要的是

将sqlite3数据库转换为mysql数据库
更改Django settings.py文件以提供MySQL数据库

在进入第一步之前，我跳到了第二个第一步。我遵循了this web page（在MacOS上）。我在根用户上创建了名为djangolocaldb的数据库，并在/etc/mysql/my.cnf中具有如下信息：

# /etc/mysql/my.cnf

[client]
database=djangolocaldb
user=root
password=ROOTPASSWORD
default-character-set=utf8

我当然创建了数据库，但没有创建表。

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| djangolocaldb      |
| employees          |
| information_schema |
| mydatabase         |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
7 rows in set (0.00 sec)

我像建议的网页一样更改了settings.py。方法如下：

# settings.py

...

# Database
# https://docs.djangoproject.com/en/3.0/ref/settings/#databases

DATABASES = {
        'default': {
            'ENGINE': 'django.db.backends.mysql',
            #'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
            'OPTIONS' : {
                'read_default_file': '/etc/mysql/my.cnf',
                }
            }
        }

...

现在，当我在激活python manage.py runserver的情况下运行venv时，我得到了这样的残酷回溯（我先运行了python manage.py migrate，回溯看起来几乎一样）：< / p>

(.venv) ➜  django-local-blog git:(master) ✗ python manage.py runserver
Watching for file changes with StatReloader
Exception in thread django-main-thread:
Traceback (most recent call last):
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/__init__.py", line 18, in <module>
    from . import _mysql
ImportError: dlopen(/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so, 2): Library not loaded: @rpath/libmysqlclient.21.dylib
  Referenced from: /Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so
  Reason: image not found

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/lib/python3.7/threading.py", line 926, in _bootstrap_inner
    self.run()
  File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/lib/python3.7/threading.py", line 870, in run
    self._target(*self._args, **self._kwargs)
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 53, in wrapper
    fn(*args, **kwargs)
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/core/management/commands/runserver.py", line 109, in inner_run
    autoreload.raise_last_exception()
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 76, in raise_last_exception
    raise _exception[1]
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/core/management/__init__.py", line 357, in execute
    autoreload.check_errors(django.setup)()
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/utils/autoreload.py", line 53, in wrapper
    fn(*args, **kwargs)
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/__init__.py", line 24, in setup
    apps.populate(settings.INSTALLED_APPS)
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/apps/registry.py", line 114, in populate
    app_config.import_models()
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/apps/config.py", line 211, in import_models
    self.models_module = import_module(models_module_name)
  File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/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 "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/contrib/auth/models.py", line 2, in <module>
    from django.contrib.auth.base_user import AbstractBaseUser, BaseUserManager
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/contrib/auth/base_user.py", line 47, in <module>
    class AbstractBaseUser(models.Model):
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/models/base.py", line 121, in __new__
    new_class.add_to_class('_meta', Options(meta, app_label))
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/models/base.py", line 325, in add_to_class
    value.contribute_to_class(cls, name)
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/models/options.py", line 208, in contribute_to_class
    self.db_table = truncate_name(self.db_table, connection.ops.max_name_length())
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/__init__.py", line 28, in __getattr__
    return getattr(connections[DEFAULT_DB_ALIAS], item)
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/utils.py", line 207, in __getitem__
    backend = load_backend(db['ENGINE'])
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/utils.py", line 111, in load_backend
    return import_module('%s.base' % backend_name)
  File "/Users/gwanghyeongim/.pyenv/versions/3.7.6/lib/python3.7/importlib/__init__.py", line 127, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/django/db/backends/mysql/base.py", line 16, in <module>
    import MySQLdb as Database
  File "/Users/gwanghyeongim/Documents/py/coreyMS_pj/django-local-blog/.venv/lib/python3.7/site-packages/MySQLdb/__init__.py", line 24, in <module>
    version_info, _mysql.version_info, _mysql.__file__
NameError: name '_mysql' is not defined

所以这是NameError: name '_mysql' is not defined的问题。我以前安装过mysqlclient，更改过settings.py，在mysql中制作了数据库，但是没有任何步骤对此有所帮助。

我注意到，即使我将settings.py改回sqlite3，我的博客也吐出了相同的 _mysql notdefined error 。因此，我最终恢复了提交，现在回到了sqlite3（至少我的博客正在运行它）。

我猜可能是我没有先转换数据，但我不确定它是100％可靠。

任何建议将不胜感激。预先谢谢你！

编辑于2020年8月18日

如果以某种方式运行_mysql not defined时仍然看到python manage.py migrate错误，请检查以下两个设置。

如果在python虚拟环境中运行mysqlclient时看到pip freeze，

(.venv) ➜  SqlDjango git:(master) ✗ pip freeze
...
Django==3.0.8
mysqlclient==2.0.1
...

确保在您的python虚拟环境中安装了mysqlclient，而不是mysql-client。前者支持python3，而后者支持python2，我认为这可能不是您想要的。

确保将以下行放入bash配置文件中（对于zsh是~/.zshrc，对于bash等是~/.bashrc或~/.bash_profile。）

export DYLD_LIBRARY_PATH=/usr/local/mysql/lib/

此后，请通过运行source ~/.your_shell_config_file应用更改。请参阅python manage.py migrate的作品。

Answer 1

这对我有用：

将其添加到 PATH：

export DYLD_LIBRARY_PATH="/usr/local/mysql/lib:$PATH"

Answer 2

所以，我在回答我自己的问题。由于我的博客具有数据库，因此我尝试了一下，使另一个没有db的项目重新开始。

我注意到在导入MySQLdb模块（mysqlclient的子模块）时出现了一个问题：Library not loaded: @rpath/libmysqlclient.21.dylib。

浏览了几个小时，我意识到由于某种原因，Mac安全设置阻止了此设置的正确导入。

在mysqlclient库github上，我发现one issue报告与我的报告相同。建议我运行cp -r /usr/local/mysql/lib/* /usr/local/lib/。在此之后，我为mysql设置settings.py，运行python manage.py migration并成功了。因此对于空数据库，这可能是一个解决方案。仍在努力与数据库一搏。

我用

MacOS Catalina 10.15.6
pyenv

Answer 3

我在 MacOS (Big Sur) 上遇到了同样的问题，我通过这样做修复了它 cp -r /usr/local/mysql/lib/* /usr/local/lib/

Answer 4

作为完整答案：

如果使用python软件包mysqlclient，则仍然需要从Oracle / MySQL安装mysql客户端。它包含python包使用的C库。让事情变得更加混乱：python包实际上是用C编写的，以提高速度。要在MacOS上安装此库，请执行以下操作：

% brew install mysql-client

还有pure python package，具有更有吸引力的MIT许可证，如果您的公司或客户不允许GPL，则可以作为解决方案。但是，它不受官方支持，并且在两个发行版之间可能会发生一些细微的错误。 YMMV。

Answer 5

这对我有用！只需安装 libmysqlclient-dev（sudo apt-get install libmysqlclient-dev 用于 Ubuntu）。有时，即使您刚刚安装了 mysql，lib 文件也会丢失。 :)

Answer 6

这为我解决了这个问题：

由于Python3无法通过mysqldb与Python连接，因此您需要安装其他模块来修复问题。安装mysqlclient导致我遇到相同的NameError: : name '_mysql' is not defined问题。

但是，通过使用pymysql并添加代码行 pymysql.install_as_MySQLdb()在我的Flask应用的顶部，我设法使其正常运行！

有关mysql modules的更多信息

Answer 7

我只是遇到了类似的问题，数小时都找不到解决方法

>>> import MySQLdb
Traceback (most recent call last):
  File "/{path-to-venv}/lib/python3.7/site-packages/MySQLdb/__init__.py", line 18, in <module>
    from . import _mysql
ImportError: /{path-to-venv}/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-arm-linux-gnueabihf.so: failed to map segment from shared object

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/{path-to-venv}/lib/python3.7/site-packages/MySQLdb/__init__.py", line 24, in <module>
    version_info, _mysql.version_info, _mysql.__file__
NameError: name '_mysql' is not defined

因此，如果这里有人像我一样，并且将virtualenv安装在已安装的分区/磁盘上，则必须使用 exec 进行安装，这就是整个问题。

按照https://askubuntu.com/questions/311438/how-to-make-tmp-executable中的说明使用可执行权限重新安装分区。

如果使用fstab安装驱动器，请参见：https://askubuntu.com/questions/678857/fstab-doesnt-mount-with-exec。

（嗯，这是经过10个小时的尝试和调试才能花掉大声笑）

Answer 8

我同意梅尔文的观点。

您可以通过键入以下内容来查看您的 MySQL 库链接：

(quantum) chaiyudeMacBook-Pro:quantum chaiyu$ python
Python 3.8.7 (v3.8.7:6503f05dd5, Dec 21 2020, 12:45:15) 
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import MySQLdb as Database
Traceback (most recent call last):
  File "/Users/chaiyu/Envs/quantum/lib/python3.8/site-packages/MySQLdb/__init__.py", line 18, in <module>
    from . import _mysql
ImportError: dlopen(/Users/chaiyu/Envs/quantum/lib/python3.8/site-packages/MySQLdb/_mysql.cpython-38-darwin.so, 2): Library not loaded: /usr/local/opt/mysql/lib/libmysqlclient.21.dylib
  Referenced from: /Users/chaiyu/Envs/quantum/lib/python3.8/site-packages/MySQLdb/_mysql.cpython-38-darwin.so
  Reason: image not found

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/chaiyu/Envs/quantum/lib/python3.8/site-packages/MySQLdb/__init__.py", line 24, in <module>
    version_info, _mysql.version_info, _mysql.__file__
NameError: name '_mysql' is not defined

然后输入：

(quantum) chaiyudeMacBook-Pro:quantum chaiyu$ otool -L /Users/chaiyu/Envs/quantum/lib/python3.8/site-packages/MySQLdb/_mysql.cpython-38-darwin.so
/Users/chaiyu/Envs/quantum/lib/python3.8/site-packages/MySQLdb/_mysql.cpython-38-darwin.so:
    /usr/local/opt/mysql/lib/libmysqlclient.21.dylib (compatibility version 21.0.0, current version 21.0.0)
    /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1252.250.1)
(quantum) chaiyudeMacBook-Pro:quantum chaiyu$ ls -l /usr/local/opt/mysql/lib/libmysqlclient.21.dylib
ls: /usr/local/opt/mysql/lib/libmysqlclient.21.dylib: No such file or directory

然后，我发现 MySQL 链接的库不存在。

Answer 9

我遇到了同样的错误，它已经工作了一段时间。我在 MacOS BigSur 上进行了更新，然后它因此错误而停止工作。

为了解决这个问题，只需重新安装 django 和 mysqlclient。

仅卸载/重新安装 mysqlclient 本身并没有解决问题。该命令也可能有所帮助。以下是我按顺序执行的命令：

pip uninstall mysqlclient
pip uninstall django
pip install django
pip install mysqlclient

注意：这将安装最新版本，因此如果您有特定版本，请确保安装这些版本。

Answer 10

从MySQL Server 8.x.x恢复到5.7.x对我有用。

Django支持MySQL 5.5.x-5.7.x。不支持MySQL 8和更高版本。

发现@ Django Docs

NameError：设置更改为mysql后未定义名称“ _mysql”

编辑于2020年8月18日

10 个答案: