A Python setup on MacOS

A memo describing how to setup a robust Python environment on MacOS >= Ventura 13.5

Know which version your system is using

python3 --version

python3 -m pip --version

At runtime :

import sys
print(sys.version_info)
print(sys.version)

Setup pyenv to manage your versions

brew install pyenv

Then basically for fish shell, add the following in config.fish :

set -g -x PYENV_ROOT $HOME/.pyenv
fish_add_path $PYENV_ROOT/bin
pyenv init - | source

echo $PATH
# outputs :
# /Users/myuser/.pyenv/shims ...

pyenv versions
# outputs :
# * system

# Requires a build environment to build Python new versions
  # xcode-select --install
  # brew install openssl readline sqlite3 xz zlib tcl-tk
pyenv install 3.12.0

pyenv version
# outputs :
# * system
# 3.12.0

# Use the 3.12.0 installed version globally
pyenv global 3.12.0

python3 --version
# outputs :
# Python 3.12.0

# to restore the system version globally
pyenv global system

Pyenv relies on the usage of so-called shims, visit https://github.com/pyenv/pyenv for further documentation

which python3
# outputs : 
# /Users/myuser/.pyenv/shims/python3

Setup your development environment

For neovim, thanks to mason plugin, you can easily provide :

# lsp server
pyright 

# tools
# python linter
ruff
# python linter and static type checker
mypy 
# python code formatter
black

Start a project with venv (virtual env)

python3 -m venv myproject

cd myproject

ls
# outputs :
# bin   include    lib    pyvenv.cfg

Activate the venv:

source bin/activate

Deactivate the venv:

deactivate

Reproducing dependencies in another venv

You can easily list your project's dependencies :

python3 -m pip list

To save all of your explicit package dependencies into a file (which, by convention, is named requirements.txt) :

# list your dependencies
python3 -m pip list

python3 -m pip freeze > requirements.txt

cat requirements.txt
# outputs :
# numpy==1.16.2
# pytz==2018.9

Then imagine you'd like to have another venv that matches the myproject environment :

python3 -m venv otherproject

cd otherproject

source bin/activate

The otherproject will have no extra packages installed :

(otherproject)$ python3 -m pip list
# outputs :
# pip 10.0.1
# setuptools 39.0.1

# install the myproject deps :
(otherproject)$ python3 -m pip install -r ../myproject/requirements.txt

# Check !
(otherproject)$ python3 -m pip list