In this article, we will upgrade to the newest python version and configure it as the default version of python. Here we use “Upgrade python 3.6 to 3.8” as an example.

Step-by-step method

Start with checking the currently installed version of Python on your system.

$ python3 -V

Python 3.6.9

Step 1: Update the package list using the below command.

$ sudo apt-get update

Step 2: Verify the updated Python packages list using this command.

$ apt list | grep python3.8

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

idle-python3.8/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 all
libpython3.8-dbg/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 amd64
libpython3.8-dev/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 amd64
libpython3.8-minimal/focal-updates,focal-security,now 3.8.10-0ubuntu1~20.04.4 amd64 [installed,automatic]
libpython3.8-stdlib/focal-updates,focal-security,now 3.8.10-0ubuntu1~20.04.4 amd64 [installed,automatic]
libpython3.8-testsuite/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 all
libpython3.8/focal-updates,focal-security,now 3.8.10-0ubuntu1~20.04.4 amd64 [installed,automatic]
python3.8-dbg/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 amd64
python3.8-dev/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 amd64
python3.8-doc/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 all
python3.8-examples/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 all
python3.8-full/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 amd64
python3.8-minimal/focal-updates,focal-security,now 3.8.10-0ubuntu1~20.04.4 amd64 [installed,automatic]
python3.8-venv/focal-updates,focal-security 3.8.10-0ubuntu1~20.04.4 amd64
python3.8/focal-updates,focal-security,now 3.8.10-0ubuntu1~20.04.4 amd64 [installed,automatic]

As seen in the image above, Now we have new version of Python available for installation.

Step 3: Install the new Python package using apt-get.
```
sudo apt-get install python3.8
```

Step 4: Add old and new version of Python to update-alternatives

sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.6 1
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.8 2

Step 5: Update Python 3 for point to Python new version.

Type this command to configure python3:

$ sudo update-alternatives --config python3

There are 2 choices for the alternative python3 (providing /usr/bin/python3).

  Selection    Path                Priority   Status
------------------------------------------------------------
* 0            /usr/bin/python3.8   2         auto mode
  1            /usr/bin/python3.6   1         manual mode
  2            /usr/bin/python3.8   2         manual mode

Press <enter> to keep the current choice[*], or type selection number: 2

You should get the above output. Now type 2 and hit enter for Python 3.8. Remember the selected number may differ so choose the selection number which is for **Python 3.**8.

Step 6: Test the version of python

Finally, test the current version of python by typing this and You should get new version of python ****as output.
```
$ python3 -V
Python 3.8.1
```