刚学习 Python 语言，运行一个现成的项目需要安装 mysqlclient，执行 pip install mysqlclient 之后，就一直报错，具体内容为：
Collecting mysqlclient
Using cached mysqlclient-2.2.0.tar.gz (89 kB)
Installing build dependencies ... done
Getting requirements to build wheel ... done
Installing backend dependencies ... done
Preparing metadata (pyproject.toml) ... done
Building wheels for collected packages: mysqlclient
Building wheel for mysqlclient (pyproject.toml) ... error
error: subprocess-exited-with-error
× Building wheel for mysqlclient (pyproject.toml) did not run successfully.
│ exit code: 1
╰─> [47 lines of output]
Trying pkg-config --exists mysqlclient
Command 'pkg-config --exists mysqlclient' returned non-zero exit status 1.
Trying pkg-config --exists mariadb
# Options for building extention module:
extra_compile_args: ['-I/opt/homebrew/Cellar/mariadb/11.1.2/include/mysql', '-std=c99']
extra_link_args: ['-L/opt/homebrew/Cellar/mariadb/11.1.2/lib', '-lmariadb', '-lssl', '-lcrypto']
define_macros: [('version_info', (2, 2, 0, 'final', 0)), ('__version__', '2.2.0')]
running bdist_wheel
running build
running build_py
creating build
creating build/lib.macosx-10.9-universal2-cpython-311
creating build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
copying src/MySQLdb/release.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
copying src/MySQLdb/cursors.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
copying src/MySQLdb/connections.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
copying src/MySQLdb/__init__.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
copying src/MySQLdb/times.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
copying src/MySQLdb/converters.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
copying src/MySQLdb/_exceptions.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
creating build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/constants
copying src/MySQLdb/constants/FLAG.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/constants
copying src/MySQLdb/constants/CLIENT.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/constants
copying src/MySQLdb/constants/__init__.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/constants
copying src/MySQLdb/constants/ER.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/constants
copying src/MySQLdb/constants/CR.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/constants
copying src/MySQLdb/constants/FIELD_TYPE.py -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/constants
running egg_info
writing src/mysqlclient.egg-info/PKG-INFO
writing dependency_links to src/mysqlclient.egg-info/dependency_links.txt
writing top-level names to src/mysqlclient.egg-info/top_level.txt
reading manifest file 'src/mysqlclient.egg-info/SOURCES.txt'
reading manifest template 'MANIFEST.in'
adding license file 'LICENSE'
writing manifest file 'src/mysqlclient.egg-info/SOURCES.txt'
copying src/MySQLdb/_mysql.c -> build/lib.macosx-10.9-universal2-cpython-311/MySQLdb
running build_ext
building 'MySQLdb._mysql' extension
creating build/temp.macosx-10.9-universal2-cpython-311
creating build/temp.macosx-10.9-universal2-cpython-311/src
creating build/temp.macosx-10.9-universal2-cpython-311/src/MySQLdb
clang -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -arch arm64 -arch x86_64 -g -I/usr/local/opt/openssl@3/include "-Dversion_info=(2, 2, 0, 'final', 0)" -D__version__=2.2.0 -I/Library/Frameworks/Python.framework/Versions/3.11/include/python3.11 -c src/MySQLdb/_mysql.c -o build/temp.macosx-10.9-universal2-cpython-311/src/MySQLdb/_mysql.o -I/opt/homebrew/Cellar/mariadb/11.1.2/include/mysql -std=c99
clang -bundle -undefined dynamic_lookup -arch arm64 -arch x86_64 -g -L/usr/local/opt/openssl@3/lib -I/usr/local/opt/openssl@3/include build/temp.macosx-10.9-universal2-cpython-311/src/MySQLdb/_mysql.o -o build/lib.macosx-10.9-universal2-cpython-311/MySQLdb/_mysql.cpython-311-darwin.so -L/opt/homebrew/Cellar/mariadb/11.1.2/lib -lmariadb -lssl -lcrypto
ld: warning: directory not found for option '-L/usr/local/opt/openssl@3/lib'
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 code 1
[end of output]
note: This error originates from a subprocess, and is likely not a problem with pip.
ERROR: Failed building wheel for mysqlclient
Failed to build mysqlclient
ERROR: Could not build wheels for mysqlclient, which is required to install pyproject.toml-based projects尝试了很多，最终原因是因为找不到我安装的 openssl，所以会出现 warning: directory not found for option '-L/usr/local/opt/openssl@3/lib' 之类的。
解决方案
查看本机 openssl 安装路径
我是通过 brew install openssl@3 安装的 openssl，安装完毕后，通过 brew --prefix openssl@3 命令查看到 openssl 的路径安装在 /opt/homebrew/opt/openssl@3 这里，并没有在 /usr/local/opt/openssl@3 这里。
指定 openssl 的位置
之后使用如下两条命令设置 openssl 的 lib 和 include 的路径
export LDFLAGS="-L/usr/local/opt/openssl@3/lib"
export CPPFLAGS="-I/usr/local/opt/openssl@3/include"再接下来执行 pip install mysqlclient 就可以顺利安装了。