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

Question

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 run 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?

Answer 1

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.

For other operating systems, click here.

Answer 2

In my case, I had to uninstall then reinstall mysql-client from Homebrew and python:

% brew reinstall mysql-client
...
% pip uninstall mysqlclient
...
% pip install mysqlclient

Why? because mysql-client was linked to libmysqlclient.22.dylib and brew upgraded it to libmysqlclient.23.dylib

Answer 3

What worked for me was using pymysql following this link and upgrading Django from 2.x to 3.x

I was not able to make it work on Django 2.x.

My configuration

1. Python 3.9
2. Apple M1 Silicon Chip
3. macOS Ventura 13.6

Answer 4

I'm using MacOS Sonoma and recently faced this issue.

I installed MySQL using homebrew. I checked the path where mysql was installed using

brew info mysql

Then I noticed that I has libmysqlclient.22.dylib instead of libmysqlclient.21.dylib which my app required. I had to create a symbolic link. In my case I had to run

ln -s /opt/homebrew/Cellar/mysql/8.1.0/lib/libmysqlclient.22.dylib /opt/homebrew/Cellar/mysql/8.1.0/lib/libmysqlclient.21.dylib

Afterwards I had to add this to my path and it worked

export DYLD_LIBRARY_PATH="/opt/homebrew/Cellar/mysql/8.1.0/lib:$DYLD_LIBRARY_PATH"

Answer 5

Please run this command

conda install -c conda-forge mysqlclient

it did it for me

Answer 6

brew install mysql

this is works for me

Answer 7

I tried all the solutions listed here and none of them worked for me.

My solution to this was to use a conda environment rather than a virtualenv. Just copy your environment to requirements.txt (for convenience) and make a new environment with conda.

1. pip freeze > requirements.txt (save your environment)
2. conda create -n django-env --file requirements.txt (create new environment)
3. pip install mysqlclient (if it wasn't already)

I was able to connect to my local mysql database and also my Amazon RDS database, no problem. I know this doesn't solve the issue directly. If you absolutely must use virtualenv this won't help.

I signed up for a Stackoverflow account just to share this. I hope it saves some other poor soul from 10 hours of "_mysql is not defined" hell.

Answer 8

M1 MacBook Pro with Ventura; working fine before then suddenly started getting this error.

TLDR:

brew link mysql-client --force

I'm not sure exactly why I started receiving this message but it was after I updated Mac OS to Ventura, did some Homebrew upgrades, and also updated Pycharm.

Checking the actual location of libmysqlclient.21.dylib and where it was being checked for showed that it simply wasn't checking the correct location.

Adding the correct location to PATH didn't fix it.

Copying the files from mysql/lib/ to /usr/local/lib/ would almost certainly fix it because I could see that location was being checked for the required file but that seems like kind of a workaround to me that might cause issues in the future...like if the package is updated in the future due to a security vulnerability but you don't notice and don't re-copy the updated files.

I could see the Homebrew directories were also being checked but Homebrew doesn't link this package by default. Trying to link it (brew link mysql-client) showed a warning that this is a keg-only package and must be linked with --force.

Double-checking with brew link mysql-client --force --dry-run showed that the command would simply link the appropriate files and wouldn't be deleting anything.

So, I thought it would be safe to go ahead and and force link it and it did indeed fix the issue for me.

Answer 9

I faced the same issue with my django project working on ubuntu 22.04 but when i imported the code below to the setting file for the django project it works,

1. import pymysql
2. pymysql.install_as_MySQLdb()

it will only work if you have pymysql installed but if you don't have it installed used pip install pymysql. This worked for me

Answer 10

For Macbook M1 this command worked

export DYLD_LIBRARY_PATH=/usr/local/mysql/lib

Answer 11

Make sure you have installed mysql client. To install it write following command.

pip install mysqlclient

Go to the settings.py file of your project and then import

import pymysql 
pymysql.install_as_MySQLdb()

run the server If you get no module named pymysql then in terminal run

pip install pymysql

Answer 12

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

Answer 13

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

Answer 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"

Answer 15

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)

Answer 16

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)

Answer 17

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

Answer 18

This worked for me

brew install mysql

Answer 19

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

Answer 20

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.

Answer 21

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.

Answer 22

this worked for me:

add this to PATH:

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

Answer 23

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/

Answer 24

Reverting back from MySQL Server 8.x.x to 5.7.x worked for me.

Django supports MySQL 5.5.x - 5.7.x. MySQL 8 and later aren’t supported.

Found @ Django Docs

Answer 25

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)

Answer 26

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

Answer 27

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.