After running pip3 install mysqlclient, the following error occurs:

ERROR: Command errored out with exit status 1:
     command: /usr/bin/python -u -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-hmicg9lo/mysqlclient_17bc9786b14e4bff9a8bdcf2c8427558/setup.py'"'"'; __file__='"'"'/tmp/pip-install-hmicg9lo/mysqlclient_17bc9786b14e4bff9a8bdcf2c8427558/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-o3rs50h8/install-record.txt --single-version-externally-managed --compile --install-headers /usr/local/include/python3.6/mysqlclient
         cwd: /tmp/pip-install-hmicg9lo/mysqlclient_17bc9786b14e4bff9a8bdcf2c8427558/
    Complete output (46 lines):
    mysql_config --version
    ['5.7.33']
    mysql_config --libs
    ['-L/usr/lib/x86_64-linux-gnu', '-lmysqlclient', '-lpthread', '-lz', '-lm', '-lrt', '-lssl', '-lcrypto', '-ldl']
    mysql_config --cflags
    ['-I/usr/include/mysql']
    ext_options:
      library_dirs: ['/usr/lib/x86_64-linux-gnu']
      libraries: ['mysqlclient', 'pthread', 'm', 'rt', 'dl']
      extra_compile_args: ['-std=c99']
      extra_link_args: []
      include_dirs: ['/usr/include/mysql']
      extra_objects: []
      define_macros: [('version_info', "(2,1,0,'final',0)"), ('__version__', '2.1.0')]
    /usr/lib/python3.6/distutils/dist.py:261: UserWarning: Unknown distribution option: 'long_description_content_type'
      warnings.warn(msg)
    /usr/lib/python3.6/distutils/dist.py:261: UserWarning: Unknown distribution option: 'python_requires'
      warnings.warn(msg)
    running install
    running build
    running build_py
    creating build
    creating build/lib.linux-x86_64-3.6
    creating build/lib.linux-x86_64-3.6/MySQLdb
    copying MySQLdb/__init__.py -> build/lib.linux-x86_64-3.6/MySQLdb
    copying MySQLdb/_exceptions.py -> build/lib.linux-x86_64-3.6/MySQLdb
    copying MySQLdb/connections.py -> build/lib.linux-x86_64-3.6/MySQLdb
    copying MySQLdb/converters.py -> build/lib.linux-x86_64-3.6/MySQLdb
    copying MySQLdb/cursors.py -> build/lib.linux-x86_64-3.6/MySQLdb
    copying MySQLdb/release.py -> build/lib.linux-x86_64-3.6/MySQLdb
    copying MySQLdb/times.py -> build/lib.linux-x86_64-3.6/MySQLdb
    creating build/lib.linux-x86_64-3.6/MySQLdb/constants
    copying MySQLdb/constants/__init__.py -> build/lib.linux-x86_64-3.6/MySQLdb/constants
    copying MySQLdb/constants/CLIENT.py -> build/lib.linux-x86_64-3.6/MySQLdb/constants
    copying MySQLdb/constants/CR.py -> build/lib.linux-x86_64-3.6/MySQLdb/constants
    copying MySQLdb/constants/ER.py -> build/lib.linux-x86_64-3.6/MySQLdb/constants
    copying MySQLdb/constants/FIELD_TYPE.py -> build/lib.linux-x86_64-3.6/MySQLdb/constants
    copying MySQLdb/constants/FLAG.py -> build/lib.linux-x86_64-3.6/MySQLdb/constants
    running build_ext
    building 'MySQLdb._mysql' extension
    creating build/temp.linux-x86_64-3.6
    creating build/temp.linux-x86_64-3.6/MySQLdb
    x86_64-linux-gnu-gcc -pthread -DNDEBUG -g -fwrapv -O2 -Wall -g -fstack-protector-strong -Wformat -Werror=format-security -Wdate-time -D_FORTIFY_SOURCE=2 -fPIC -Dversion_info=(2,1,0,'final',0) -D__version__=2.1.0 -I/usr/include/mysql -I/usr/include/python3.6m -c MySQLdb/_mysql.c -o build/temp.linux-x86_64-3.6/MySQLdb/_mysql.o -std=c99
    MySQLdb/_mysql.c:46:20: fatal error: Python.h: No such file or directory
    compilation terminated.
    error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
    ----------------------------------------
ERROR: Command errored out with exit status 1: /usr/bin/python -u -c 'import io, os, sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-hmicg9lo/mysqlclient_17bc9786b14e4bff9a8bdcf2c8427558/setup.py'"'"'; __file__='"'"'/tmp/pip-install-hmicg9lo/mysqlclient_17bc9786b14e4bff9a8bdcf2c8427558/setup.py'"'"';f = getattr(tokenize, '"'"'open'"'"', open)(__file__) if os.path.exists(__file__) else io.StringIO('"'"'from setuptools import setup; setup()'"'"');code = f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-o3rs50h8/install-record.txt --single-version-externally-managed --compile --install-headers /usr/local/include/python3.6/mysqlclient Check the logs for full command output.

 

Solution:

sudo apt-get install python3.6-dev

It may be due to the mismatch of dev version due to the installation of Python 3.6 in Ubuntu.