问题背景：

Mac下打开terminal，输入以下代码安装mysqlclient

pip3 install mysqlclient

输出错误日志内容：

  Using cached mysqlclient-1.3.12.tar.gz
Installing collected packages: mysqlclient
  Running setup.py install for mysqlclient: started
    Running setup.py install for mysqlclient: finished with status 'error'
    Complete output from command /Library/Frameworks/Python.framework/Versions/3.6/bin/python3.6 -u -c "import setuptools, tokenize;__file__='/private/var/folders/4k/68mf14qn3gx0pb4wt6hg6p7r0000gn/T/pycharm-packaging/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 /var/folders/4k/68mf14qn3gx0pb4wt6hg6p7r0000gn/T/pip-e1yq85ib-record/install-record.txt --single-version-externally-managed --compile:
    running install
    running build
    running build_py
    creating build
    creating build/lib.macosx-10.6-intel-3.6
    copying _mysql_exceptions.py -> build/lib.macosx-10.6-intel-3.6
    creating build/lib.macosx-10.6-intel-3.6/MySQLdb
    copying MySQLdb/__init__.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb
    copying MySQLdb/compat.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb
    copying MySQLdb/connections.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb
    copying MySQLdb/converters.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb
    copying MySQLdb/cursors.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb
    copying MySQLdb/release.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb
    copying MySQLdb/times.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb
    creating build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    copying MySQLdb/constants/__init__.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    copying MySQLdb/constants/CLIENT.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    copying MySQLdb/constants/CR.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    copying MySQLdb/constants/ER.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    copying MySQLdb/constants/FIELD_TYPE.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    copying MySQLdb/constants/FLAG.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    copying MySQLdb/constants/REFRESH.py -> build/lib.macosx-10.6-intel-3.6/MySQLdb/constants
    warning: build_py: byte-compiling is disabled, skipping.
    
    running build_ext
    building '_mysql' extension
    creating build/temp.macosx-10.6-intel-3.6
    /usr/bin/clang -fno-strict-aliasing -Wsign-compare -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -arch i386 -arch x86_64 -g -Dversion_info=(1,3,12,'final',0) -D__version__=1.3.12 -I/usr/local/Cellar/mysql/5.7.21/include/mysql -I/Library/Frameworks/Python.framework/Versions/3.6/include/python3.6m -c _mysql.c -o build/temp.macosx-10.6-intel-3.6/_mysql.o
    /usr/bin/clang -bundle -undefined dynamic_lookup -arch i386 -arch x86_64 -g build/temp.macosx-10.6-intel-3.6/_mysql.o -L/usr/local/Cellar/mysql/5.7.21/lib -lmysqlclient -lssl -lcrypto -o build/lib.macosx-10.6-intel-3.6/_mysql.cpython-36m-darwin.so
    ld: library not found for -lssl
    clang: error: linker command failed with exit code 1 (use -v to see invocation)
    error: command '/usr/bin/clang' failed with exit status 1

网上搜索了很多未找到明确解决方案，最终到官方github相关issue中找到解决方法：

https://github.com/PyMySQL/mysqlclient-python/issues/169

Github给出brew info openssl的解释：
解决方法：
添加环境变量：

export LDFLAGS="-L/usr/local/opt/openssl/lib"
export CPPFLAGS="-I/usr/local/opt/openssl/include"

环境变量创建、编辑、保存:

1. 启动终端Terminal

2. 进入当前用户的home目录

   输入cd ~

3. 创建.bash_profile

   输入touch .bash_profile

4. 编辑.bash_profile文件

   输入open -e .bash_profile

5. 保存文件，关闭.bash_profile

6. 更新刚配置的环境变量

   输入source .bash_profile

最终重新输入pip3 install mysqlclient可看到成功安装

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