The Python Launcher for UNIX

An implementation of the py command for UNIX-based platforms.

The goal is to have py become the cross-platform command that all Python users use when executing a Python interpreter. Not only is it short and to the point, but it also provides a single command that documentation can use in examples which will work regardless of what operating system a user is on. Lastly, it side-steps the "what should the python command point to?" debate by clearly specifying that upfront (i.e. the newest version of Python that is installed).

Search order

py -3.6

1. Search PATH for python3.6

py -3

1. Use the PY_PYTHON3 environment variable if defined (e.g. PY_PYTHON3=3.6)
2. Search PATH for all instances of python3.Y
3. Find the executable with largest Y

py

1. Use the PY_PYTHON environment variable if defined (e.g. PY_PYTHON=3) version requested and search accordingly
2. Search PATH for all instances of pythonX.Y
3. Find the executable with largest X.Y version

TODO

NOTE: I am using this project to learn Rust, so please don't be offended if I choose to implement something myself instead of accepting a pull request that you submit. (Pull requests to do something I have already implemented in a more idiomatic fashion are very much appreciated, though.)

PEP 397: Python launcher for Windows (documentation)

• Virtual environment takes precedence when no version specified (VIRTUAL_ENV)
• Shebang line parsing
  • Only the first argument if it's a file and doesn't start with -
  • Not necessary, but nice to have
• PYLAUNCH_DEBUG
• py -0
  • Output well-formatted JSON to start in order for it to be consumable?
  • Output column format like pip list?
• py -h emits its own help before continuing on to call python
• Configuration files
  • Customized commands
  • Want a better format like TOML?
  • Want to use Pipfile and its python_version field?
  • Probably want a way to override things, e.g. wanting a framework build on macOS somehow
    • Aliasing? E.g. 2.7-framework=/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python?
    • Just provide a way to specify a specific interpreter for a specific version? E.g. 2.7=/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python