I have a running Django blog with sqlite3 db at my local machine. What I want is to

1. convert sqlite3 db to mysql db
2. change Django settings.py file to serve MySQL db

Before I ran into the first step, I jumped into the second first. I followed this web page (on MacOS). I created databases called djangolocaldb on root user and have those infos in /etc/mysql/my.cnf like this:

# /etc/mysql/my.cnf [client] database=djangolocaldb user=root password=ROOTPASSWORD default-character-set=utf8

Of course I created db, but not table within it.

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

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I changed settings.py like this as the web page suggested. Here’s how:

# 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’, } } } …

Now, when I ran python manage.py runserver with my venv activated, I got a brutal traceback like this(I ran python manage.py migrate first, and the traceback looked almost the same anyway):

(.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

So this NameError: name ‘_mysql’ is not defined is the problem. I installed mysqlclient before, changed settings.py, made db in mysql, but none of the steps made it any helpful yet.

And I noticed that even I changed my settings.py back to sqlite3, my blog spit the same _mysql not defined error. So I ended up reverting my commit and now I’m back to sqlite3 (at least my blog is running with it).

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I’m guessing it could be that I didn’t convert data first, but I’m not 100% sure of it.

Any suggestion would be much appreciated. Thank you in advance!

If you still see _mysql not defined error when you run python manage.py migrate somehow, check out the following two settings.

1. If you see mysqlclient when you run pip freeze in your python virtual environment like so,

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

make sure you installed mysqlclient in your python virtual environment, not mysql-client. The former supports python3, whereas the latter supports python2, which I assume is not probably what you want.

1. Make sure you put the following line in your bash config file(~/.zshrc for zsh, or ~/.bashrc or ~/.bash_profile for bash etc.)

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

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After that, apply change by runnig source ~/.your_shell_config_file. See python manage.py migrate works.

So as a full answer:

If you use the python package mysqlclient you still need to install the mysql client from Oracle/MySQL. This contains the C-library that the python package uses. To make things more confusing: the python package is in fact written in C for speed increases. To install this library on MacOS:

% brew install mysql-client

There’s also a pure python package, with a more attractive MIT License, which can be a solution if your company or client does not allow GPL. However, it’s not officially supported and some subtle bugs can occur in between releases. YMMV.

Answered By – user1600649