本机的python从2.7升级到3.7后，mysqldb这个包就失效了，一直无法使用，由于用的少，也就没去管。今天答应帮朋友个小忙要用到mysql，所以打算把这个搁置了很久的小问题解决掉，以便后面可以继续用。
首先，其实python升级到3.7之后，原来的mysqldb已经不支持了，需要换成mysqlclient（地址戳我）
Mac系统安装步骤：
1. brew install mysql-client
2. pip install mysqlclient
以上步骤很简单，但在pip install mysqlclient的时候报错如下：
ERROR: Command errored out with exit status 1:
command: /Users/Allen/Documents/workSpace/PythonPack/ventpy3/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/nm/yd1zh7p54xb5t9wsb73j846w0000gp/T/pip-install-pf8mmrsv/mysqlclient/setup.py'"'"'; __file__='"'"'/private/var/folders/nm/yd1zh7p54xb5t9wsb73j846w0000gp/T/pip-install-pf8mmrsv/mysqlclient/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /private/var/folders/nm/yd1zh7p54xb5t9wsb73j846w0000gp/T/pip-record-9bmrkgmw/install-record.txt --single-version-externally-managed --compile --install-headers /Users/Allen/Documents/workSpace/PythonPack/ventpy3/include/site/python3.7/mysqlclient
cwd: /private/var/folders/nm/yd1zh7p54xb5t9wsb73j846w0000gp/T/pip-install-pf8mmrsv/mysqlclient/
Complete output (32 lines):
/usr/local/Cellar/python/3.7.4/Frameworks/Python.framework/Versions/3.7/lib/python3.7/distutils/dist.py:274: UserWarning: Unknown distribution option: 'long_description_content_type'
warnings.warn(msg)
running install
running build
running build_py
creating build
creating build/lib.macosx-10.14-x86_64-3.7
creating build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/__init__.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/_exceptions.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/compat.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/connections.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/converters.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/cursors.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/release.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
copying MySQLdb/times.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb
creating build/lib.macosx-10.14-x86_64-3.7/MySQLdb/constants
copying MySQLdb/constants/__init__.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb/constants
copying MySQLdb/constants/CLIENT.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb/constants
copying MySQLdb/constants/CR.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb/constants
copying MySQLdb/constants/ER.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb/constants
copying MySQLdb/constants/FIELD_TYPE.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb/constants
copying MySQLdb/constants/FLAG.py -> build/lib.macosx-10.14-x86_64-3.7/MySQLdb/constants
running build_ext
building 'MySQLdb._mysql' extension
creating build/temp.macosx-10.14-x86_64-3.7
creating build/temp.macosx-10.14-x86_64-3.7/MySQLdb
clang -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/usr/include -I/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk/System/Library/Frameworks/Tk.framework/Versions/8.5/Headers -I/usr/local/opt/mysql-client/include -Dversion_info=(1,4,6,'final',0) -D__version__=1.4.6 -I/usr/local/Cellar/mysql/8.0.18/include/mysql -I/Users/Allen/Documents/workSpace/PythonPack/ventpy3/include -I/usr/local/Cellar/python/3.7.4/Frameworks/Python.framework/Versions/3.7/include/python3.7m -c MySQLdb/_mysql.c -o build/temp.macosx-10.14-x86_64-3.7/MySQLdb/_mysql.o
clang -bundle -undefined dynamic_lookup -L/usr/local/opt/mysql-client/lib -I/usr/local/opt/mysql-client/include build/temp.macosx-10.14-x86_64-3.7/MySQLdb/_mysql.o -L/usr/local/Cellar/mysql/8.0.18/lib -lmysqlclient -lssl -lcrypto -o build/lib.macosx-10.14-x86_64-3.7/MySQLdb/_mysql.cpython-37m-darwin.so
ld: library not found for -lssl
clang: error: linker command failed with exit code 1 (use -v to see invocation)
error: command 'clang' failed with exit status 1
----------------------------------------
ERROR: Command errored out with exit status 1: /Users/Allen/Documents/workSpace/PythonPack/ventpy3/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/private/var/folders/nm/yd1zh7p54xb5t9wsb73j846w0000gp/T/pip-install-pf8mmrsv/mysqlclient/setup.py'"'"'; __file__='"'"'/private/var/folders/nm/yd1zh7p54xb5t9wsb73j846w0000gp/T/pip-install-pf8mmrsv/mysqlclient/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /private/var/folders/nm/yd1zh7p54xb5t9wsb73j846w0000gp/T/pip-record-9bmrkgmw/install-record.txt --single-version-externally-managed --compile --install-headers /Users/Allen/Documents/workSpace/PythonPack/ventpy3/include/site/python3.7/mysqlclient Check the logs for full command output.
最终发现，其实是openssl没有指明配置路径，解决方法如下：
export LDFLAGS="-L/usr/local/opt/openssl/lib $LDFLAGS"
export CPPFLAGS="-I/usr/local/opt/openssl/include $CPPFLAGS"
完成后再执行pip install mysqlclient即可！
