Linux学习笔记：安装python
一般linux自带python2，如果需要python3以上版本，可以不需要卸载自带的python2，二者可以共存。只需要配置相应的环境变量即可。
具体回答可以参考这篇文章 https://stackoverflow.com/questions/26282986/how-to-update-python-2-7-to-python-3-in-linux
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Python 2 and 3 can safely be installed together. They install most of their files in different locations. So if the prefix is /usr/local, you'll find the library files in /usr/local/lib/pythonX.Y/ where X.Y are the major and minor version numbers.
The only point of contention is generally is the file python itself, which is generally a symbolic link.
Currently it seems most operating systems still use Python 2 as the default, which means that python is a symbolic link to python2. This is also recommended in the Python documentation.
It is best to leave it like that for now. Some programs in your distributions may depend on this, and might not work with Python 3.
So install Python 3 (3.5.1 is the latest version at this time) using your favorite package manager or compiling it yourself. And then use it by starting python3 or by putting #!/usr/bin/env python3 as the first line in your Python 3 scripts and making them executable (chmod +x <file>)
上面内容的大意是：python2和3可以共存，可以安装在不同的位置。例如 /usr/local/lib/pythonX.Y，这X.Y代表了主要版本。而需要配置全局环境变量其实就是python这个文件自身，它可以是一个快捷方式。
如果需要执行依赖python3的python脚本，只需要要在文件第一行加上 #!/usr/bin/env python3 ，或者加上#!/usr/bin/python3。二者的区别可以见这篇文章 https://www.jianshu.com/p/400c612381dd
如果提示 /usr/bin/python^M: bad interpreter: No such file or directory，这是因为windows和linux行尾标识符不同，可以用文本编辑工具File - Conversions - DOS - UNIX，或者 Edit - EOL Conversion -UNIX(LF)。
如何安装python3版本：
yum install epel-release
yum install python36
上面的python36是仓库中的最新版本，后面可能会更新到37等更高的版本。
