Manage virtual environments

https://www.cnblogs.com/yibeimingyue/p/13833966.html
https://blog.csdn.net/better_boy/article/details/107063421

1. Create a virtual environment with python=2.7
   conda create -n py27 python=2.7

2. View a list of environmental
   conda env list

3. Start and exit the virtual environment
   conda activate py27
   conda deactivate

4. View package information in the
   current environment To view all installed packages in the current environment, you can use:
   conda list

5. Install and uninstall third-party packages for a standalone environment
   conda install numpy
   pip uninstall numpy

6. Delete the entire virtual environment
   conda remove -n py27 --all