Python Environment Setup with pyenv and venv

Setup for python development environment. We will use pyenv (version manager) + venv instead of conda.

Setup pyenv

This section is for the installation of pyenv itself. It should be only done once per machine.

Install pyenv and dependencies with package manager according to the official suggested build environment.
Mac OS
```
brew install openssl readline sqlite3 xz zlib tcl-tk
```
Initialize pyenv so the shell uses it by default
```
pyenv init # Follow the instructions outputted
```
I put mine in the login shell (.zprofile) instead of the interactive shell settings.
See which versions of python is available for install
```
pyenv install -l
```
Install one of the versions
```
pyenv install 3.11 # Installs the latest revision of python 3.11
```
If you encounter dependency errors such as missing lzma lib, it maybe because the dependency in step1 is not configured properly.
Set global python version
```
pyenv global 3.11
```
Relogin / restart shell.

Verify installation

which python # Should output ~/.pyenv/shims/python instead of /bin/python
python --version # Should output previously set global python version

This section is for project environment setup. It should be done for every project.

To start, make sure you're in the project directory.

Install the correct python version if needed (optonal).
```
pyenv install <PYTHON_VERSION>
```
Set the local python version (optional)
```
pyenv local <PYTHON_VERSION> # Will overwrite .python-version
```
This binds the python version to project directory by creating .python-version in the directory.

Create virtual environment

python -m venv .venv # Creates virtual environment at the .venv/ folder
echo ".venv" >> .gitignore # Add it to .gitignore

Activate the venv and verify

source .venv/bin/activate
which python # Should output <PROJECT>/.venv/bin/python

Upgrade pip
```
python -m pip install --upgrade pip
```
If its an existing project that has requirements.txt, install the requirements. (optional)
```
python -m pip install -r requirements.txt
```

Extras:

Freeze the project requirements into requirements.txt
```
python -m pip freeze > requirements.txt
```

Update all outdated packages

pip list -o | tail -n +3 | awk '{ print $1 }' | xargs pip install -U