Installing Python as local user on Linux – Zentera Systems

This is a cheat-sheet-style article based on information found on other online resources including manuals for Python, Virtual Environments, StackOverflow articles, etc

Objective:

A bare Centos 7 or Ubuntu comes with Python 2 and Python 3.8. We need Python 3.9
Some OS utilities may install Python 3 as dependencies. Don't want to touch them to not break anything else
Hence, installing under local user will side step any dependency conflicts and allow a dedicated Python3.9 installation that can be used for Zapy SDK
Benefit - removing/reinstalling/upgrading this local Python3 installation becomes simple

Steps

With sudo/root privileges for this step only, install OS level dependency packages

CentOS
sudo yum install gcc zlib zlib-devel bzip2 bzip2-devel readline-devel sqlite sqlite-devel openssl-devel xz xz-devel libffi libffi-devel lzma
Ubuntu
sudo apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev libssl-dev libreadline-dev libffi-dev libsqlite3-dev wget libbz2-dev

NOTE - If you are missing some of these dependencies, and still try to install python, you might have to reinstall..!
For the rest of these steps, do not use sudo/root
Python3.9 installation as regular user

version=3.9.12
version_short=3.9

wget https://www.python.org/ftp/python/$version/Python-$version.tgz
tar xzf Python-$version.tgz
cd Python-$version
./configure --enable-optimizations --enable-shared --prefix=$HOME/python$version LDFLAGS=-Wl,-rpath=$HOME/python$version/lib
make -j 8 # for faster build time j is number of cores to use. Get number from nproc
make altinstall # so it does not trash installed python2 or other system-preinstalled python version
python$version_short -V

echo "export PATH=$HOME/python$version/bin/:$PATH" >> ~/.bashrc
echo "export PYTHONPATH=$HOME/python$version/bin" >> ~/.bashrc

export PATH=$HOME/python$version/bin/:$PATH
export PYTHONPATH=$HOME$version/python/bin

Virtual Environment configuration as regular user

~/python$version/bin/python$version_short -m venv ~/venv_3
source ~/venv_3/bin/activate
pip install --upgrade pip setuptools

# optional:
echo "source ~/venv_3/bin/activate" >> ~/.bashrc

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