问题
I have a brand new django 2.2.1 project I have just installed into a python 3.7 virtualenv on OS X (10.14.4). After some frustrations I got mysqlclient to install but when I run the django dev server it doesn't recognise that it is installed:
Here are the steps I've taken so far:
brew install mysql
pipenv --three
pipenv install django==2.2.1
pipenv install mysqlclient
brew uninstall mysql
brew install mysql-connector-c
pipenv install mysqlclient
brew unlink mysql-connector-c
brew install mysql
django-admin startproject projectname
Now, the only change I have made to the out-of-the-box django installation is to change the default database backend to django.db.backends.mysql and when I run the django server I get the following:
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module.
Did you install mysqlclient?
However, going back to the virtualenv and doing "pip install mysqlclient" gives:
Requirement already satisfied: mysqlclient in /Users/<username>/.local/share/virtualenvs/<projectname>-KrUE_JNo/lib/python3.7/site-packages (1.4.2.post1)
Any ideas why django can't see the mysqlclient installed in the virtualenv? I can confirm that all of the above has been run in the virtualenv. I suspect it has something to do with the faff that OSX makes you go through to install it but I'm not sure how to pick it apart.
I have also tried to replace mysqldb with pymysql as suggested here but that causes the server to give a different error:
raise ImproperlyConfigured('mysqlclient 1.3.13 or newer is required; you have %s.' % Database.__version__)
django.core.exceptions.ImproperlyConfigured: mysqlclient 1.3.13 or newer is required; you have 0.9.3.
Mysql is a given for this project so use of an alternative backend is not an option. Any help very gratefully received, many thanks in advance.
UPDATE: Output of pip freeze:
Django==2.2.1
django-auth-ldap==1.7.0
Markdown==3.1
mysql-connector-python==8.0.16
mysqlclient==1.4.2.post1
protobuf==3.7.1
pyasn1==0.4.5
pyasn1-modules==0.2.5
PyMySQL==0.9.3
pyodbc==4.0.26
python-ldap==3.2.0
pytz==2019.1
simplejson==3.16.0
six==1.12.0
sqlparse==0.3.0
xmltodict==0.12.0
UPDATE 2: Following conor's post (thanks conor) I started again with a fresh virtualenv and again successfully installed mysqlclient1.4.2.post1. Here's the output from pip freeze now:
Django==2.2.1
mysqlclient==1.4.2.post1
pytz==2019.1
sqlparse==0.3.0
Still getting the same error when I do python manage.py runserver though:
django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module.
Did you install mysqlclient?
UPDATE 3: Thought I would try importing the MySQLdb module on the python command line to see if I can get any more insight and it returns the following:
>>> import MySQLdb
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/Users/<username>/.local/share/virtualenvs/<projectname>-KrUE_JNo/lib/python3.7/site-packages/MySQLdb/__init__.py", line 18, in <module>
from . import _mysql
ImportError: dlopen(/Users/<username>/.local/share/virtualenvs/<projectname>-KrUE_JNo/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so, 2): Symbol not found: _mysql_affected_rows
Referenced from: /Users/<username>/.local/share/virtualenvs/<projectname>-KrUE_JNo/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so
Expected in: flat namespace
in /Users/<username>/.local/share/virtualenvs/<projectname>-KrUE_JNo/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so
回答1:
SOLVED
So it looks like the issue was that on initial installation the mysqlclient library had compiled against the wrong version of mysql (not sure how that happened), so I had to force it to recompile.
Here are the steps:
brew uninstall mysql
brew uninstall myysql-connector-c
pipenv uninstall mysqlclient
brew install mysql-connector-c
At this point we need to update /usr/local/bin/mysql_config as per the instructions that conor linked to (thanks again conor), i.e. change the line that read
libs="$libs -l "
to
libs="$libs -lmysqlclient -lssl -lcrypto "
Then, to fix the resultant "library not found for -lssl" error I used the answer from this question:
export PATH="/usr/local/opt/openssl/bin:$PATH"
export LDFLAGS="-L/usr/local/opt/openssl/lib"
export CPPFLAGS="-I/usr/local/opt/openssl/include"
Then finally force mysqlclient to recompile and reinstall mysql:
pip install --force-reinstall --ignore-installed --no-binary :all: mysqlclient
brew unlink mysql-connector-c
brew install mysql
Thanks to everyone who took time to help out!
回答2:
If you're on macos do this
$ brew uninstall mysql
$ brew install mysql-connector-c
$ brew unlink mysql-connector-c
$ brew install mysql
$ pip install mysql-python
and follow the instructions here: https://pypi.org/project/mysqlclient/
回答3:
Downgrading from python 3.7.4 to python 3.6 solved the issue for me on windows 10.
来源：https://stackoverflow.com/questions/56115144/fresh-python-3-7-django-2-2-1-installation-not-recognising-that-mysqlclient-is