'NameError: name '_mysql' is not defined after setting change to mysql

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)

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).

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!

EDITED on Aug 18, 2020

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/

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

pythonmysqldjangodatabasesqlite


Solution 1:[1]

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.

Solution 2:[2]

This did the job for me! Just install libmysqlclient-dev (sudo apt-get install libmysqlclient-dev for Ubuntu). Sometimes, the lib files simply are missing even if you just installed mysql. :)

Solution 3:[3]

So, I'm answering my own question. Since my blog has database, I gave it a shot to make another project without db, start fresh.

What I noticed was there's a problem importing MySQLdb module(sub module of mysqlclient) with this traceback: Library not loaded: @rpath/libmysqlclient.21.dylib.

For browsing a few hours I realised that for some reason Mac security setting keeps this from being imported properly.

On mysqlclient library github I found one issue reporting the same as mine. It suggests I run cp -r /usr/local/mysql/lib/* /usr/local/lib/. After this I set settings.py for django.db.backends.mysql, ran python manage.py migrate and it worked. So for empty database, this could be a solution. Still struggling with database one though.

I use

  • MacOS Catalina 10.15.6
  • pyenv

Solution 4:[4]

this worked for me:

add this to PATH:

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

Solution 5:[5]

I was facing the same problem on my MacOS (Big Sur) and I fixed it by doing this cp -r /usr/local/mysql/lib/* /usr/local/lib/

Solution 6:[6]

This solved the issue for me:

Since Python3 is not able to connect with Python through mysqldb, you need to install an additional module to fix things. installing mysqlclient caused me to have the same NameError: : name '_mysql' is not defined problem.

However, by using pymysql, and adding the code line pymysql.install_as_MySQLdb() at the top of my Flask app, I managed to get it running without any errors!

More info on mysql modules

Solution 7:[7]

I just had a similar problem and couldnt find solution for hours

>>> 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

so if anyone here is like me and has the virtualenv on a mounted partition/disk, you have to mount it with exec, thats the whole problem.

Remount the partition with executable permission as explained in: https://askubuntu.com/questions/311438/how-to-make-tmp-executable.

If you mount the drive with fstab, see: https://askubuntu.com/questions/678857/fstab-doesnt-mount-with-exec.

(well, that was 10hours of trying and debugging well spend lol)

Solution 8:[8]

I agree with Melvyn.

you can see your MySQL library link by typing like:

(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

then type:

(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

and then, I found the library MySQL linked to does not exist.

Solution 9:[9]

I had the same error and it was working for a while. I did an update on MacOS BigSur then it stopped working with this error.

To fix this for me it was a simple uninstall reinstall of both django and mysqlclient.

The uninstall/reinstall of just mysqlclient itself did not do the trick. Also the order may help. Here are the commands in the order i did it in:

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

Note: this will install the latest versions, so if you have specific versions, make sure you install those versions.

Solution 10:[10]

This worked for me

brew install mysql

Solution 11:[11]

for mac

Assume you are activating Python 3 venv

brew install mysql
pip install mysqlclient

for ubuntu interminal run

sudo apt-get install python3-dev default-libmysqlclient-dev build-essential
pip install mysqlclient

for # Red Hat / CentOS

sudo yum install python3-devel mysql-devel
pip install mysqlclient

Solution 12:[12]

Finally after spending like decade on this issue found a good answer.

mysqlclient is a Python 3 compatible fork of the original Python MySQL driver, MySQLdb. It still provides a Python module called MySQLdb. On install, it compiles against either the MariaDB client library or MySQL client library - whichever one you have installed.

Solution Found Here By Adam(Genius Guy)

Solution 13:[13]

From Apple Silicon M1 Mac and a conda environment the only solution that worked for me was to use Miniforge installation, which is comparable to Miniconda, but with conda-forge as the default channel. There is an Apple Silicon option that solved the problem for me: https://github.com/Haydnspass/miniforge#download

(Solution from https://towardsdatascience.com/using-conda-on-an-m1-mac-b2df5608a141)

Solution 14:[14]

If you're using bash, use:

open -t .bash_profile

and add the following:

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

If you're using Zsh, use:

open -t ~/.zshrc

and add the following:

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

Solution 15:[15]

although I used _mysql for 10 years, the MySQL website tells the recommended way for Python 3 at: https://dev.mysql.com/doc/connector-python/en/preface.html

Conversion may take some time, but for me less than an hour. Here an example with new code:

import mysql.connector
cnx = mysql.connector.connect(user='mensfort', password='zhongcan',
                              host='127.0.0.1', database='restaurant')
cursor = cnx.cursor()
cursor.execute('select dongle from personnel')
for dongle in cursor:
    print(dongle)
cursor.close()
cnx.close()

Please use your own password, database name, queries, this is just an example.

Please do UNINSTALL this. This is not working for me:

pip uninstall mysql-connector

Please INSTALL this first. It works great:

pip install mysql-connector-python

Solution 16:[16]

On a MacBook Pro M1 macOS Monterey, running this command didn't work:

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

But this worked for me:

export DYLD_LIBRARY_PATH=/usr/local/mysql/lib

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