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
测试是否安装成功：
>> 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.
virutalenv安装成功了。
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。