【背景】

　　今天我把算把自己的python基礎平臺從python-3.6.2升級到python-3.7.2，在我安裝完python-3.7.2之後，打算在此基礎之上安裝

　　mysqlclient的時候報錯了；

pip3 install mysqlclient
Collecting mysqlclient
  Downloading https://files.pythonhosted.org/packages/de/d7/919042fb7ed78a89e21c4e43d5daed90d5df18ec183bae3de493a7d9e3ed/mysqlclient-1.4.1.tar.gz (85kB)
    100
 
% |████████████████████████████████| 92kB 33kB/s 
Installing collected packages: mysqlclient
  Running setup.py install for mysqlclient ... error
    Complete output from command /Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 -u -c "import setuptools, tokenize;__file__=‘/private/tmp/pip-install-27wftw10/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/tmp/pip-record-678j2sqk/install-record.txt --single-version-externally-managed --compile:
    running install
    running build
    running build_py
    creating build
    creating build/lib.macosx-10.9-x86_64-3.7
    creating build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb
 
/__init__.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb/_exceptions.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb/compat.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb/connections.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb/converters.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb/cursors.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb/release.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    copying MySQLdb/times.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb
    creating build/lib.macosx-10.9-x86_64-3.7/MySQLdb/constants
    copying MySQLdb/constants/__init__.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb/constants
    copying MySQLdb/constants/CLIENT.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb/constants
    copying MySQLdb/constants/CR.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb/constants
    copying MySQLdb/constants/ER.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb/constants
    copying MySQLdb/constants/FIELD_TYPE.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb/constants
    copying MySQLdb/constants/FLAG.py -> build/lib.macosx-10.9-x86_64-3.7/MySQLdb/constants
    running build_ext
    building ‘MySQLdb._mysql‘ extension
    creating build/temp.macosx-10.9-x86_64-3.7
    creating build/temp.macosx-10.9-x86_64-3.7/MySQLdb
    gcc -Wno-unused-result -Wsign-compare -Wunreachable-code -fno-common -dynamic -DNDEBUG -g -fwrapv -O3 -Wall -arch x86_64 -g -Dversion_info=(1,4,1,‘final‘,0) -D__version__=1.4.1 -I/usr/local/homebrew/Cellar/mysql/8.0.12/include/mysql -I/Library/Frameworks/Python.framework/Versions/3.7/include/python3.7m -c MySQLdb/_mysql.c -o build/temp.macosx-10.9-x86_64-3.7/MySQLdb/_mysql.o
    gcc -bundle -undefined dynamic_lookup -arch x86_64 -g build/temp.macosx-10.9-x86_64-3.7/MySQLdb/_mysql.o -L/usr/local/homebrew/Cellar/mysql/8.0.12/lib -lmysqlclient -lssl -lcrypto -o build/lib.macosx-10.9-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 ‘gcc‘ failed with exit status 1
    
    ----------------------------------------
Command "/Library/Frameworks/Python.framework/Versions/3.7/bin/python3.7 -u -c "import setuptools, tokenize;__file__=‘/private/tmp/pip-install-27wftw10/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/tmp/pip-record-678j2sqk/install-record.txt --single-version-externally-managed --compile" failed with error code 1 in /private/tmp/pip-install-27wftw10/mysqlclient/
You are using pip version 18.1, however version 19.0.1 is available.
You should consider upgrading via the ‘pip install --upgrade pip‘ command.

【問題分析】

　　從上面的內容可以看出安裝過程中加載不了目標庫文件 lssl ，而這個是openssl的軟件包中的內容、我把上面日誌中關鍵的幾行摘下來

    ld: library not found for -lssl
    clang: error: linker command failed with exit code 1 (use -v to see invocation)
    error: command ‘gcc‘ failed with exit status 1

　　這下就冤有頭債有主了、我只要告訴gcc庫文件和連接文件都在哪裏就行了、由於我是用homebrew進行包管理的、info一下就會有答案了

brew config openssl
Usage: brew config

Show Homebrew and system configuration useful for debugging. If you file
a bug report, you will likely be asked for this information if you do not
provide it.

    -v, --verbose                    Make some output more verbose.
    -d, --debug                      Display any debugging information.
    -h, --help                       Show this message.

Error: Invalid usage
JianglexingdeMacBook-Pro:~ jianglexing$ brew info openssl
openssl: stable 1.0.2p [keg-only]
SSL/TLS cryptography library
https://openssl.org/
/usr/local/homebrew/Cellar/openssl/1.0.2n (1,784 files, 12.3MB)
  Built from source on 2018-01-07 at 11:30:02
/usr/local/homebrew/Cellar/openssl/1.0.2o_2 (1,784 files, 12.3MB)
  Built from source on 2018-08-13 at 13:12:02
/usr/local/homebrew/Cellar/openssl/1.0.2p (1,785 files, 12.3MB)
  Built from source on 2018-08-23 at 14:05:54
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/openssl.rb
==> Dependencies
Build: makedepend ?
==> Options
--without-test
    Skip build-time tests (not recommended)
==> Caveats
A CA file has been bootstrapped using certificates from the SystemRoots
keychain. To add additional certificates (e.g. the certificates added in
the System keychain), place .pem files in
  /usr/local/homebrew/etc/openssl/certs

and run
  /usr/local/homebrew/opt/openssl/bin/c_rehash

openssl is keg-only, which means it was not symlinked into /usr/local/homebrew,
because Apple has deprecated use of OpenSSL in favor of its own TLS and crypto libraries.

If you need to have openssl first in your PATH run:
  echo ‘export PATH="/usr/local/homebrew/opt/openssl/bin:$PATH"‘ >> ~/.bash_profile

For compilers to find openssl you may need to set:
  export LDFLAGS="-L/usr/local/homebrew/opt/openssl/lib"
  export CPPFLAGS="-I/usr/local/homebrew/opt/openssl/include"

For pkg-config to find openssl you may need to set:
  export PKG_CONFIG_PATH="/usr/local/homebrew/opt/openssl/lib/pkgconfig"

　　我還是把上面日誌中關鍵的信息摘一下吧；現在問題的解決方案就非常的清楚了，把下面的那兩個export運行一下

For compilers to find openssl you may need to set:
  export LDFLAGS="-L/usr/local/homebrew/opt/openssl/lib"
  export CPPFLAGS="-I/usr/local/homebrew/opt/openssl/include"

【解決問題】

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


pip3 install mysqlclient
Collecting mysqlclient
  Using cached https://files.pythonhosted.org/packages/de/d7/919042fb7ed78a89e21c4e43d5daed90d5df18ec183bae3de493a7d9e3ed/mysqlclient-1.4.1.tar.gz
Installing collected packages: mysqlclient
  Running setup.py install for mysqlclient ... done
Successfully installed mysqlclient-1.4.1
You are using pip version 18.1, however version 19.0.1 is available.
You should consider upgrading via the ‘pip install --upgrade pip‘ command.

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Mac上安裝mysqlclient的報錯