引言： 在目前的Linux系统中，默认使用的都是Python 2.7.x的版本环境，如何想要在其上基于Python3的环境来进行开发，则需要基于VirutalEnv来构建独立的开发环境。

1. 环境介绍

CentOS 7,Python 2.7,Python 3.6

2. 下载安装virutalenv

>> pip install virtualenv

[root@xxxl]# ^C
[root@xxxZ]# pip install virtualenv
Collecting virtualenv
  Downloading http://mirrors.aliyun.com/pypi/packages/6f/86/3dc328ee7b1a6419ebfac7896d882fba83c48e3561d22ddddf38294d3e83/virtualenv-15.1.0-py2.py3-none-any.whl (1.8MB)
    100% |████████████████████████████████| 1.8MB 34.9MB/s 
Installing collected packages: virtualenv
Successfully installed virtualenv-15.1.0

>> virtualenv -h

[root@xxx]# virtualenv -h
Usage: virtualenv [OPTIONS] DEST_DIR

Options:
  --version             show program's version number and exit
  -h,--help            show this help message and exit
  -v,--verbose         Increase verbosity.
  -q,--quiet           Decrease verbosity.
  -p PYTHON_EXE,--python=PYTHON_EXE
                        The Python interpreter to use,e.g.,--python=python2.5 will use the python2.5 interpreter
                        to create the new environment.  The default is the
                        interpreter that virtualenv was installed with
                        (/usr/bin/python2)
  --clear               Clear out the non-root install and start from scratch.
  --no-site-packages    DEPRECATED. Retained only for backward compatibility.
                        Not having access to global site-packages is now the
                        default behavior.
  --system-site-packages
                        Give the virtual environment access to the global
                        site-packages.
  --always-copy         Always copy files rather than symlinking.
  --unzip-setuptools    Unzip Setuptools when installing it.
  --relocatable         Make an EXISTING virtualenv environment relocatable.
                        This fixes up scripts and makes all .pth files
                        relative.
  --no-setuptools       Do not install setuptools in the new virtualenv.
  --no-pip              Do not install pip in the new virtualenv.
  --no-wheel            Do not install wheel in the new virtualenv.
  --extra-search-dir=DIR
                        Directory to look for setuptools/pip distributions in.
                        This option can be used multiple times.
  --download            Download preinstalled packages from PyPI.
  --no-download,--never-download
                        Do not download preinstalled packages from PyPI.
  --prompt=PROMPT       Provides an alternative prompt prefix for this
                        environment.
  --setuptools          DEPRECATED. Retained only for backward compatibility.
                        This option has no effect.
  --distribute          DEPRECATED. Retained only for backward compatibility.
                        This option has no effect.

3. 安装新的Python版本

可以从python的官方站点，下载源代码，编译安装，这里Python安装包是3.6.1的版本。具体的安装过程可以参考网路上的文档。

4. VirtualEnv的设置

>> virutalenv -p python36-install-path python36env

这里设置Python版本为3.6， 新的环境目录为python36env

>> source python36env/bin/activate # 激活虚拟环境

>> deactivate # 退出当前的虚拟环境

5. 总结

这个隔离的环境非常方便，进行程序的开发和环境的切换。