Change version of "python" and "pip" command

If you want use Python3.5 with a command "python", we need to create "symbolic link" for python3.5. We will check the directory of Python:

$ sudo ls -l /bin/py*

And we will change those symbolic links:

$ sudo ln -s /bin/python3.5 /bin/python3 
$ sudo unlink /bin/python 
$ sudo ln -s /bin/python3 /bin/python

pip also.

$ sudo ln -s /bin/pip3.5 /bin/pip

And it's done!