• virtualenv is a tool to create isolated Python environments.
  • The basic problem being addressed is one of dependencies and versions, and indirectly permissions. Imagine you have an application that needs version 1 of LibFoo, but another application requires version 2. How can you use both these applications? If you install everything into /usr/lib/python2.7/site-packages (or whatever your platform’s standard location is), it’s easy to end up in a situation where you unintentionally upgrade an application that shouldn’t be upgraded.
  • virtualenv就是用来为一个应用创建一套“隔离”的Python运行环境
  • 典型的一种场景就是你的机器上同时需要运行Python2和Python3两个版本的Python,那么用virtualenv可以非常方便地管理不同版本的Python
  • 当然,更多的时候virtualenv也被用来创建同一Python版本+不同版本第三方库的运行环境。


pip install virtualenv

CentOS 7上安装Python3

  • yum install epel-release
  • 或者 wget -O /etc/yum.repos.d/epel.repo
  • yum install python34
  • 检查安装 $ python3
  • 升级刚刚安装的virtualenv: pip install –upgrade virtualenv (here was a bug in the OP’s version of virtualenv, so we run this command to fix it)



  • virtualenv env2x # 使用Python2创建环境
  • cd env2x
  • source ./bin/activate # 进入
  • 使用你的python2环境
  • deactivate # 退出


  • virtualenv –p python3 env3x # 使用Python3创建环境
  • cd env3x
  • source ./bin/activate # 进入
  • 使用你的python3环境
  • deactivate # 退出


virtualenv是如何创建“独立”的Python运行环境的呢?原理很简单,就是把系统Python复制一份到virtualenv的环境,用命令source venv/bin/activate进入一个virtualenv环境时,virtualenv会修改相关环境变量,让命令python和pip均指向当前的virtualenv环境。