[windows版]Python创建虚拟环境并更新升级pip

目标：Python 虚拟环境用于将软件包安装与系统隔离开来。

先创建一个虚拟环境：

python -m venv  .\venv

激活虚拟环境：

.\venv\Scripts\activate

升级 pip： 

(venv_pyqt) D:\venvs>pip list
Package    Version
---------- -------
pip        19.2.3
setuptools 41.2.0
WARNING: You are using pip version 19.2.3, however version 21.3.1 is available.
You should consider upgrading via the 'python -m pip install --upgrade pip' command.

(venv_pyqt) D:\venvs>python -m pip install --upgrade pip
Collecting pip
  Using cached https://files.pythonhosted.org/packages/a4/6d/6463d49a933f547439d6b5b98b46af8742cc03ae83543e4d7688c2420f8b/pip-21.3.1-py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 19.2.3
    Uninstalling pip-19.2.3:
      Successfully uninstalled pip-19.2.3
Successfully installed pip-21.3.1

(venv_pyqt) D:\venvs>pip list
Package    Version
---------- -------
pip        21.3.1
setuptools 41.2.0

(venv_pyqt) D:\venvs>                                      

退出该虚拟环境：

deactivate