Install almost all Python environments on Ubuntu 20.04

install-python.sh

#! /bin/bash
#
# Copyright (c) 2020 Víctor Molina García
# MIT License
#
# Script to install Python environments 2.6+ and 3.2+ using PyEnv
# and the installation steps for OpenSSL 1.0.2 mostly based on the
# information available in the following link:
#     http://www.linuxfromscratch.org/blfs/view/7.7/postlfs/openssl.html
#
# Tested on Ubuntu 20.04; bash is required because otherwise the PyEnv
# initialisation command fails.
#

# Set to exit on error.
set -e
cwd=$(pwd)

# Install basic dependencies.
echo "Installing basic dependencies..."
sudo apt-get install -y build-essential wget curl llvm git libssl-dev tk-dev  \
                        libncursesw5-dev libreadline-dev libsqlite3-dev       \
                        libffi-dev xz-utils zlib1g-dev libbz2-dev liblzma-dev

sudo apt-get install -y openssl ca-certificates

# Download and install OpenSSL 1.0.2.
openssl_name=openssl-1.0.2
openssl_targz=$openssl_name.tar.gz
openssl_patch=$openssl_name-fix_parallel_build-1.patch
openssl_dir=$HOME/.local/opt/$openssl_name
openssl_inc=$openssl_dir/include
openssl_lib=$openssl_dir/lib
openssl_ssl=$openssl_dir/ssl

echo "Downloading OpenSSL..."
wget https://www.openssl.org/source/$openssl_targz
wget https://www.linuxfromscratch.org/patches/downloads/openssl/$openssl_patch

echo "Decompressing OpenSSL..."
tar -xf $openssl_targz

echo "Patching OpenSSL..."
cd $openssl_name
patch -Np1 -i ../$openssl_patch

echo "Installing OpenSSL..."
./config --prefix=$openssl_dir --openssldir=$openssl_dir/ssl --libdir=lib     \
         -Wl,-rpath=$openssl_dir/lib shared zlib-dynamic
make
make install

cd $cwd
rm -rf $openssl_name

echo "Linking CA certificates..."
rmdir $openssl_ssl/certs && ln -s /etc/ssl/certs $openssl_ssl/certs

# Download PyEnv from its GitHub repository.
export PYENV_ROOT=$HOME/.local/share/pyenv
export PATH=$PYENV_ROOT/bin:$PATH
git clone https://github.com/pyenv/pyenv.git $HOME/.local/share/pyenv
eval "$(pyenv init -)"
echo "Installing all Pythons..."

# Install Python versions that can use OpenSSL v1.1.
pyenv install 3.9.0
pyenv install 3.8.6
pyenv install 3.7.9
pyenv install 3.6.12
pyenv install 3.5.10
pyenv install 2.7.18

# Install Python versions that require the elder OpenSSL v1.0.2.
export CFLAGS="-I$openssl_inc"
export LDFLAGS="-L$openssl_lib"
export LD_LIBRARY_PATH="$openssl_lib"
pyenv install 3.4.10
pyenv install 3.3.7
pyenv install 3.2.6
pyenv install 2.6.9

echo "Remember to set LD_LIBRARY_PATH=$openssl_lib in your .bashrc file:"
echo "    LD_LIBRARY_PATH=$openssl_lib:\$LD_LIBRARY_PATH"

@ewertao Thanks! I have just updated the gist.