Python's MySQLdb can’t find libmysqlclient.dylib with Homebrewed MySQL

问题

MySQL and Python installed with Homebrew

I installed MySQL and Python with Homebrew on OS X 10.10.5 Yosemite. My Python 2.7 is at python -> ../Cellar/python/2.7.9/bin/python with a symlink to it at /usr/local/bin/python.

In /usr/local/bin there is a symlink:
mysql -> ../Cellar/mysql/5.7.9/bin/mysql

The error

In the Python shell:

>>> import MySQLdb
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/site-packages/MySQLdb/__init__.py", line 19, in <module>
    import _mysql
ImportError: dlopen(/usr/local/lib/python2.7/site-packages/_mysql.so, 2): Library not loaded: /usr/local/lib/libmysqlclient.18.dylib
  Referenced from: /usr/local/lib/python2.7/site-packages/_mysql.so
  Reason: image not found

So I tried:
$ sudo unlink /usr/local/lib/libmysqlclient.18.dylib

followed by:
DYLD_LIBRARY_PATH=/usr/local/mysql/lib/:$DYLD_LIBRARY_PATH

and then (desperation over reason):
$ export DYLD_LIBRARY_PATH=/usr/local/Cellar/mysql/5.7.9/lib

But in both cases import MySQLdb still tried to import libmysqlclient.18.dylib.

Then I tried:
$ pip install -U MySQL-python and got: Requirement already up-to-date: MySQL-python in /usr/local/lib/python2.7/site-packages

Existing answers

Many answers to this problem on SO suggest manually making an explicit symlink to the library with a version number (in my case libmysqlclient.20.dylib). However, this seems crude and not future-proof, given the existing symlinks:

in /usr/local/lib there is
libmysqlclient.dylib -> ../Cellar/mysql/5.7.9/lib/libmysqlclient.dylib

and in /usr/local/Cellar/mysql/5.7.9/lib we find:
libmysqlclient.20.dylib

with a symlink in the same directory to it: libmysqlclient.dylib -> libmysqlclient.20.dylib

How to make Python forget libmysqlclient.18.dylib?

So how can I get Python to forget /usr/local/lib/libmysqlclient.18.dylib and follow the correct symlink in in /usr/local/lib to libmysqlclient.dylib, without manually adding yet another symlink?

回答1:

This solved my issue on my case:

$ pip uninstall MySQL-python
$ pip install mysqlclient

MySQL-python turned out to be very old (last commit was 7 years ago). mysqlclient is the modern version of it, with lots of improvements and bug fixes.

回答2:

I also encountered this problem. I uninstalled the MySQL-python, and then installed it.

pip uninstall MySQL-python
pip install MySQL-python

---

Update (based on comments)

In some cases, you may need to perform the second (install) step in the following manner:

pip install --no-binary MySQL-python MySQL-python

The no-binary option is so that pip builds it fresh and links to the correct library:

--no-binary <format_control>

Do not use binary packages. Can be supplied multiple times, and each time adds to the existing value. Accepts either :all: to disable all binary packages, :none: to empty the set, or one or more package names with commas between them. Note that some packages are tricky to compile and may fail to install when this option is used on them.

NB: Note, that MySQL-python needs to be mentioned twice. As mentioned above, the first occurrence is the name of the package to apply the no-binary option to, the second specifies the package to install.

回答3:

You need to use dev version of mysqlclient:

pip install git+https://github.com/PyMySQL/mysqlclient-python.git@master

Before I had the lastest PyPI version (1.3.7) on Python 3.4 and it was searching for libmysqlclient.18.dylib (from MySQL 5.6) whereas I had only libmysqlclient.20.dylib(from MySQL 5.7).

If you use Python 3, MySQL-python is not an option (and mysqlclient is its newer version).

回答4:

If encountered a problem with lacking of libmysqlclient.18.dylib:

1. download mysql 5.6 from official link: https://dev.mysql.com/downloads/mysql/

2. install it

3. in terminal - mdfind libmysqlclient | grep .18.

4. copy the output

5. sudo ln -s [the output from previous command] /usr/local/lib/libmysqlclient.18.dylib

来源：https://stackoverflow.com/questions/34536914/pythons-mysqldb-can-t-find-libmysqlclient-dylib-with-homebrewed-mysql