使用venv设置python虚拟环境

Beginning with Python 3.4, venv (a stdlib alternative to virtualenv) will create virtualenv environments with pip pre-installed, thereby making it an equal alternative to virtualenv.

1. cmd进入指定路径，输入 python -m venv venv_name (创建虚拟环境)
2. > cd .\venv_name\Scripts
3. > activate.bat (激活和使用该虚拟环境)
4. > deactivate.bat (退出该虚拟环境)