You can update by using following commands:
sudo apt-get install python3
(or)
sudo apt-get upgrade
Download python-3.x version from the python.org
Extract .tar.gz using the command tar xvf Python-3.x.tar.gz
goto that directory using cd dir_name
$./configure
$sudo make
$sudo make install
in that you will get an error for pip it requires ssl
install the service using this command
$sudo apt-get install libssl-dev openssl
after that again install using $sudo make install
After that use python3 command to open interpreter
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