我们使用python virtualenv构建不同的python环境，python3 也加入了virtualenv 模块。
virtualenvwrapper 提供了更便捷的 virtualenv环境的生命周期管理功能，使用起来很skr！
(3.6) ➜ site-packages virtualenvwrapper
virtualenvwrapper is a set of extensions to Ian Bicking's virtualenv
tool. The extensions include wrappers for creating and deleting
virtual environments and otherwise managing your development workflow,
making it easier to work on more than one project at a time without
introducing conflicts in their dependencies.
For more information please refer to the documentation:
http://virtualenvwrapper.readthedocs.org/en/latest/command_ref.html
Commands available:
add2virtualenv: add directory to the import path
allvirtualenv: run a command in all virtualenvs
cdproject: change directory to the active project
cdsitepackages: change to the site-packages directory
cdvirtualenv: change to the $VIRTUAL_ENV directory
cpvirtualenv: duplicate the named virtualenv to make a new one
lssitepackages: list contents of the site-packages directory
lsvirtualenv: list virtualenvs
mkproject: create a new project directory and its associated virtualenv
mktmpenv: create a temporary virtualenv
mkvirtualenv: Create a new virtualenv in $WORKON_HOME
rmvirtualenv: Remove a virtualenv
setvirtualenvproject: associate a project directory with a virtualenv
showvirtualenv: show details of a single virtualenv
toggleglobalsitepackages: turn access to global site-packages on/off
virtualenvwrapper: show this help message
wipeenv: remove all packages installed in the current virtualenv
workon: list or change working virtualenvs
这是virtualenvwrapper 的文档：
https://virtualenvwrapper.readthedocs.io/en/latest/command_ref.html
另外2个env管理工具
pipenv：更侧重于python项目的包管理
https://github.com/pypa/pipenv
pyenv：简单的python 版本管理工具