依次执行如下命令：需要root权限，普通用户可以使用sudo 来执行以下命令
root@ubuntu-server:~# add-apt-repository ppa:fkrull/deadsnakes
root@ubuntu-server:~# apt-get update
root@ubuntu-server:~# apt-get install python3.5
root@ubuntu-server:~# python
Python 2.7.6 (default, Jun 22 2015, 17:58:13)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()
这样就安装好了，不过由于环境变量的影响，因此，默认情况下，输入python进入的是python2.7.6，输入python3进入的是python3.4，只有输入python3.5才进入到python3.5。因此我们可以根据需要做以下更改：
root@ubuntu-server:~# ln -s /usr/bin/python3.5 /usr/bin/python35
root@ubuntu-server:~# python35
Python 3.5.3 (default, Apr 22 2017, 00:00:00)
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
root@ubuntu-server:~# mv /usr/bin/python3 /usr/bin/python34
root@ubuntu-server:~# python34
Python 3.4.3 (default, Oct 14 2015, 20:28:29)
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>>
安装pip
root@ubuntu-server:~# wget https://bootstrap.pypa.io/get-pip.py
root@ubuntu-server:~# python35 get-pip.py
root@ubuntu-server:~# pip3 install setuptools –upgrade
root@ubuntu-server:~# pip -V
pip 9.0.1 from /usr/local/lib/python3.5/dist-packages (python 3.5)
新手小白初学Python，如有错误之处，欢迎指正。