一般在使用pip install xxx之后会有黄色的提示信息，提示当前pip版本过低，请升级到最近版本，并给出了升级命令；

You are using pip version 19.0.3, however version 22.2.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.

pip install --upgrade pip -i http://pypi.douban.com/simple/

DEPRECATION: Configuring installation scheme with distutils config files is deprecated and will no longer work in the near future. If you are using a Homebrew or Linuxbrew Python, please see discussion at https://github.com/Homebrew/homebrew-core/issues/76621
Looking in indexes: http://pypi.douban.com/simple/
Requirement already satisfied: pip in /usr/local/lib/python3.7/site-packages (22.2.2)
WARNING: The repository located at pypi.douban.com is not a trusted or secure host and is being ignored. If this repository is available via HTTPS we recommend you use HTTPS instead, otherwise you may silence this warning and allow it anyway with '--trusted-host pypi.douban.com'.
DEPRECATION: Configuring installation scheme with distutils config files is deprecated and will no longer work in the near future. If you are using a Homebrew or Linuxbrew Python, please see discussion at https://github.com/Homebrew/homebrew-core/issues/76621

提示需要增加 ‘–trusted-host pypi.douban.com’

pip3 install --upgrade pip -i http://pypi.douban.com/simple/ --trusted-host pypi.douban.com

Looking in indexes: http://pypi.douban.com/simple/
Collecting pip
  Downloading http://pypi.doubanio.com/packages/1f/2c/d9626f045e7b49a6225c6b09257861f24da78f4e5f23af2ddbdf852c99b8/pip-22.2.2-py3-none-any.whl (2.0MB)
    100% |████████████████████████████████| 2.0MB 39.2MB/s 
Installing collected packages: pip
  Found existing installation: pip 19.0.3
    Uninstalling pip-19.0.3:
      Successfully uninstalled pip-19.0.3
Successfully installed pip-22.2.2

输入pip3 -V验证一下pip版本：

pip -V

pip 22.2.2 from /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-packages/pip (python 3.7)

OK，更新成功！