python 3.9 on debian buster

python 3.9 on debian buster

sudo apt-get install build-essential checkinstall
sudo apt-get install libreadline-gplv2-dev libncursesw5-dev libssl-dev \
    libsqlite3-dev tk-dev libgdbm-dev libc6-dev libbz2-dev libffi-dev zlib1g-dev
    
wget https://www.python.org/ftp/python/3.9.0/Python-3.9.0.tgz
tar xzf Python-3.9.0.tgz

cd Python-3.9.0
 ./configure --enable-optimizations --prefix=/opt/python/3.9
 make -j$(nproc)
 sudo make altinstall
 
export PATH=/opt/python/3.9/bin:$PATH

or create your venv

/opt/python/3.9/bin/python3.9 -m venv venv
source venv/bin/activate