导读：
我们先使用python -v来测试一下当前版本：
ortonwu@ubuntu:~$ python -V
Python 2.7
...
我们先使用python -v来测试一下当前版本：
ortonwu@ubuntu:~$ python -V Python 2.7
升级或安装Python3的话，可以使用如下命令下载最新的Python:
apt-get install python3
之后输入python可以进入python的命令行交互：
ortonwu@ubuntu:/usr/bin$ python Python 2.7.12 (default, Nov 19 2016, 06:48:10) [GCC 5.4.0 20160609] on linux2 Type "help", "copyright", "credits" or "license" for more information.>>>
这里显示的Python版本是2.7，而不是刚下载的3.5。这是因为python被软连接到python2.7了。可以在/usr/bin下查看python link文件：
ortonwu@ubuntu:~$ ll /usr/bin/ | grep ^l | grep python lrwxrwxrwx 1 root root 26 Apr 1 20:11 dh_pypy -> ../share/dh-python/dh_pypy*lrwxrwxrwx 1 root root 29 Apr 1 20:11 dh_python3 -> ../share/dh-python/dh_python3*lrwxrwxrwx 1 root root 23 Nov 19 01:36 pdb2.7 -> ../lib/python2.7/pdb.py*lrwxrwxrwx 1 root root 23 Nov 17 11:26 pdb3.5 -> ../lib/python3.5/pdb.py*lrwxrwxrwx 1 root root 31 Apr 1 20:11 py3versions -> ../share/python3/py3versions.py*lrwxrwxrwx 1 root root 26 Apr 1 20:11 pybuild -> ../share/dh-python/pybuild*lrwxrwxrwx 1 root root 18 Apr 25 07:43 python -> /usr/bin/python3.5*lrwxrwxrwx 1 root root 9 Apr 1 20:11 python2 -> python2.7*lrwxrwxrwx 1 root root 9 Apr 1 20:11 python3 -> python3.5*lrwxrwxrwx 1 root root 10 Apr 1 20:11 python3m -> python3.5m*lrwxrwxrwx 1 root root 29 Apr 1 20:11 pyversions -> ../share/python/pyversions.py*
重新建立到python3.5的软连接即可：
ortonwu@ubuntu:/usr/bin$ sudo rm -rf python ortonwu@ubuntu:/usr/bin$ sudo ln -s /usr/bin/python3.5 /usr/bin/python
这时使用python即可进入python3.5命令行交互界面：
ortonwu@ubuntu:/usr/bin$ python Python 3.5.2 (default, Nov 17 2016, 17:05:23) [GCC 5.4.0 20160609] on linux Type "help", "copyright", "credits" or "license" for more information.>>>
本文转载来源：https://www.tfyum.net/news.html?nid=3&id=1559
