配置 python/pip 命令环境变量：

安装完成后，其实在终端可以执行 python/pip，只是由于安装的 python3，其命令是 python3/pip3：

Air ~ % pip3 -V
pip 21.2.3 from /Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/pip (python 3.9)

使用 python/pip 命令：

在终端使用 which 命令查找 python/pip 执行文件路径:

Air ~ % which python3 
/Library/Frameworks/Python.framework/Versions/3.9/bin/python3
Air ~ % which pip3   
/Library/Frameworks/Python.framework/Versions/3.9/bin/pip3

编辑 bash_profile 文件

vim 打开bash_profile

vi ~/.bash_profile

按i，进入insert模式，将python3 路径写入：

PATH="/Library/Frameworks/Python.framework/Versions/3.9/bin:${PATH}"
export PATH
alias python="/Library/Frameworks/Python.framework/Versions/3.9/bin/python3"
PATH="/Library/Frameworks/Python.framework/Versions/3.9/bin:${PATH}"
export PATH
alias pip="/Library/Frameworks/Python.framework/Versions/3.9/bin/pip3"
export PATH=/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin/
export PATH=${PATH}:/usr/local/bin/chromedriver

按esc, 输入英文模式：“:wq!”，按Enter，退出bash_profile

更新bash_profile

Air ~ % source ~/.bash_profile

查看使用pip安装的包（site-packages目录的位置）

python查看自己的第三方库默认安装路径

Air ~ % python -m site
sys.path = [
    '/Users/用户名',
    '/Library/Frameworks/Python.framework/Versions/3.9/lib/python39.zip',
    '/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9',
    '/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib-dynload',
    '/Users/用户名/Library/Python/3.9/lib/python/site-packages',
    '/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages',
]
USER_BASE: '/Users/用户名/Library/Python/3.9' (exists)
USER_SITE: '/Users/用户名/Library/Python/3.9/lib/python/site-packages' (exists)
ENABLE_USER_SITE: True