This short guide explains how to install Python 3.9.4 on a Raspberry Pi running Raspbian.
First install the dependencies needed to build
sudo apt-get update
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
Compile (takes a while!)wget https://www.python.org/ftp/python/3.9.4/Python-3.9.4.tar.xz
tar xf Python-3.9.4.tar.xz
cd Python-3.9.4
./configure --prefix=/usr/bin/python3.9.4
make -j 4
Installsudo make altinstall
And remove the files
cd ..
rm -r Python-3.9.4
rm Python-3.9.4.tar.xz
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.9.2 1
sudo update-alternatives --set python /usr/bin/python3.9.2
And verify:python -V