how to update python in raspberry pi

I need python newest version in raspberry pi.
I tried apt install python3 3.8
apt install python3 but this didnot work.
And I also needed to update my raspberry pi python IDLE

Answer

First update the Raspbian.

sudo apt-get update    

Then install the prerequisites that will make any further installation of Python and/or packages much smoother.

sudo apt-get install -y build-essential tk-dev libncurses5-dev libncursesw5-dev libreadline6-dev libdb5.3-dev libgdbm-dev libsqlite3-dev libssl-dev libbz2-dev libexpat1-dev liblzma-dev zlib1g-dev libffi-dev

And then install Python, maybe by downloading a compressed file?

example 1 :

wget https://www.python.org/ftp/python/3.8.0/Python-3.8.0.tgz    

Extract the folder :

sudo tar zxf Python-3.8.0.tgz

Move into the folder :

cd Python-3.8.0

Initial configuration :

sudo ./configure --enable-optimizations

Run the makefile inside the folder with the mentioned parameters :

sudo make -j 4

Run again the makefile this time installing directly the package :

sudo make altinstall

Maybe You already did it but You don’t know how to setup the new version as a default version of the system?

Check first that it has been installed :

python3.8 -V

Send a strong command to .bashrc telling him who (which version) is in charge of Python

echo "alias python=/usr/local/bin/python3.8" >> ~/.bashrc

Again! Tell him because .bashrc has to understand! I am joking – You have to source the file so the changes can be applied immediately :

source ~/.bashrc

And then check that Your system changed the default version of Python to Python 3.8

python -V

The failure depends on many factors : what dependencies are installed, what are the packages added to the source_list.d, some inconvenient coming up during the installation. All may give you more information than you think, just read carefully. Hope it helped.