Install python 3.6 on your RPi!

python-3.6-pi.sh

#!/usr/bin/bash

putsc() {
    echo -en "\e[34m :: \e[0m $@"
}

putscl() {
    putsc "$@\n"
}

cores="$(ncores)"

putscl "Which Python version do you wish to download? (3.6.0, 3.6.4 etc.) "

read version

putscl Updating system.
sudo apt update
sudo apt upgrade

putscl Installing required build dependencies.

sudo apt install 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 -y

putscl Downloading Python $version source code.

pushd

mkdir -p $HOME/.local/src
cd $HOME/.local/src

wget https://www.python.org/ftp/python/$version/Python-$version.tar.xz
tar xvf Python-$version.tar.xz
cd Python-$version

putscl Configuring.

./configure

putscl Compiling.

make -j$cores

putscl Installing.

sudo make altinstall

putsc "Installation done! Do you wish to delete the source code? [Y/n] "

read ans

if [[ ans == [Yy]* ]]
then
sudo rm -r Python-$version
rm Python-$version.tar.xz
sudo apt autoremove
sudo apt clean
fi

popd

putscl "Done! Python should now be installed in `/usr/local/bin/python$version`!"

build-essential is used for gcc, make, header files and other stuff required for development. Here it's used to compile py 3.6.0

I get your point, I don't understand why previous me had that in the script, maybe to remove bloat if you dont need it? Doesn't matter though since you can just say N

Updated the script to make the output nicer and fixed some bugs.