在 python3 import 時的錯誤訊息：
Chuns-MacBook-Pro:mysqlclient chunyuyao$ python3
Python 3.7.0 (default, Jul 23 2018, 20:22:55)
[Clang 9.1.0 (clang-902.0.39.2)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
from MySQLdb import _mysql
Traceback (most recent call last):
File "", line 1, in
File "/usr/local/lib/python3.7/site-packages/MySQLdb/init.py", line 18, in
from . import _mysql
ImportError: dlopen(/usr/local/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so, 2): Library not loaded: /usr/local/opt/mysql/lib/libmysqlclient.20.dylib
Referenced from: /usr/local/lib/python3.7/site-packages/MySQLdb/_mysql.cpython-37m-darwin.so
Reason: image not found
實際到 /usr/local/opt/mysql/lib/ 去 ls 結果：
-rw-r--r-- 1 chunyuyao staff 5419384 Mar 3 02:17 libmysqlclient.21.dylib
-r--r--r-- 1 chunyuyao staff 6052712 Jan 26 06:50 libmysqlclient.a
lrwxr-xr-x 1 chunyuyao staff 23 Jan 26 06:50 libmysqlclient.dylib -> libmysqlclient.21.dylib
-rw-r--r-- 1 chunyuyao staff 565184 Mar 3 02:17 libmysqlharness.1.dylib
-r--r--r-- 1 chunyuyao staff 1060048 Jan 26 06:50 libmysqlharness.a
lrwxr-xr-x 1 chunyuyao staff 23 Jan 26 06:50 libmysqlharness.dylib -> libmysqlharness.1.dylib
-r--r--r-- 1 chunyuyao staff 6140608 Mar 3 02:17 libmysqlrouter.1.dylib
lrwxr-xr-x 1 chunyuyao staff 22 Jan 26 06:50 libmysqlrouter.dylib -> libmysqlrouter.1.dylib
-r--r--r-- 1 chunyuyao staff 9760 Jan 26 06:50 libmysqlservices.a
drwxr-xr-x 7 chunyuyao staff 224 Jan 26 06:50 mysqlrouter
drwxr-xr-x 3 chunyuyao staff 96 Mar 3 02:17 pkgconfig
drwxr-xr-x 98 chunyuyao staff 3136 Jan 26 06:50 plugin
應該是在 macOS 裡執行 brew upgrade 导致 mysql 有檔案不見，解法：
ln -s libmysqlclient.21.dylib libmysqlclient.20.dylib
brew install mysql 不只讓python3 出錯，python2 也壞掉，我的環境錯誤訊息：
ImportError: dlopen(/Library/Python/2.7/site-packages/_mysql.so, 2): Library not loaded: /usr/local/opt/mariadb/lib/libmysqlclient.18.dylib
Referenced from: /Library/Python/2.7/site-packages/_mysql.so
Reason: image not found
解法，先讓 /usr/local/opt/mysql link to /usr/local/opt/mariadb
再 ln -s libmysqlclient.21.dylib libmysqlclient.18.dylib
搞定。 ^_^
測試的方法，分別使用 python2 和 python3 測試下面這行指令：
import MySQLdb
接下來，是連進 mysql 裡：
Python 連 mysql
https://stackoverflow.max-everyday.com/2017/09/python-mysql/