Recent versions of Ubuntu Linux include Python 3 out of the box, so no installation is required.By default both Python 2 and Python 3 are already installed on Linux
In Linux python is for Python2.x version and python3 is for Python3.x version
Python can be installed from source
$ wget https://www.python.org/ftp/python/3.7.0/Python-3.7.0a2.tgz
$ tar -zxvf Python-3.7.0a2.tgz
$ cd Python-3.7.0a2
$ ./configure
$ make
$ make test
$ make install
Note: If you are not having admin access , run install command with sudo