argparsenv

argparsenv

This project extends python's argparse module to allow for environment variable overrides of command line arguments.

The rule for environment variable overrides is as follows:

• If the argument is provided on the command line, the environment variable is ignored.
• If the argument is not provided on the command line, the environment variable is used if it is set.
• If the argument is not provided on the command line and the environment variable is not set, the default value is used.
• If the argument is environment variable is set both on the command line and in the environment, the command line value is used.

Installation

Stable release version:

pip install argparsenv

Latest development version:

pip install git+https://github.com/snaeil/argparsenv

Usage

This module builds on top of python's standard library argparse.

import argparsenv

env_arg_parser = ArgumentParser()
env_arg_parser.add_argument(
    "--port",
    dest="port",
    env_var="MY_APP_DB_PORT",
    default="3306",
)

With this ArgumentParser instance, the port argument can be set in three ways:

• On the command line:

python my_app.py --port 3307

• As an environment variable (this can also be done by using a .env file):

export MY_APP_DB_PORT=3307
python my_app.py

• Using the default value (here 3306):

python my_app.py

Contributing

Contributions are welcome! For feature requests, bug reports or questions, please open an issue. For code contributions, please open a pull request.

The development environment can be set up using nix and devenv:

• Install nix package manager: bash <(curl -L https://nixos.org/nix/install) --no-daemon
• Make sure, your ~/.config/nix/nix.conf contains the following lines:

  experimental-features = nix-command flakes
  

• Install devenv by running:

  nix profile install --accept-flake-config 'nixpkgs#devenv'
  

• Install nix-direnv by running:

  nix profile install 'nixpkgs#nix-direnv'
  

  Then add nix-direnv to $HOME/.config/direnv/direnvrc:

  source $HOME/.nix-profile/share/nix-direnv/direnvrc
  

• Hook direnv into your shell by adding a line to your shell's configuration file (e.g. ~/.bashrc), as described in the direnv documentation:
• You might have to open a new shell to make the changes take effect.