brettcannon/ python-launcher

Rust

Python

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brettcannon

142 Stars

6 Forks

MIT License

376 Commits

9 Opened issues

Description

Python launcher for Unix

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Readme

The Python Launcher for Unix

Name: python-launcher
Brand: python-launcher
SKU: //brettcannon/python-launcher
Rating: 2.105 (142 reviews)

An implementation of the

py

command for Unix-based platforms (with some potential experimentation for good measure 😉)

The goal is to have

py

become the cross-platform command that all Python users use when executing a Python interpreter. By having a version-agnostic command 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 can be found). This also unifies the suggested command to document for launching Python on both Windows as Unix as

py

which has existed as the preferred command on Windows for some time.

See the top section of

py --help

for instructions.

Installation

You can either install from crates.io or from source. Both approaches require you install the Rust toolchain. You can use rustup to accomplish this or whatever your OS suggests.

If you want to install from crates.io, run:

cargo install python-launcher

If you want to install from source, run:

cargo install --path .

Search order

Please note that while searching, the search for a Python version can become more specific. This leads to a switch in the search algorithm to the one most appropriate to the specificity of the version.

You can always run the Python Launcher with

PYVENV_DEBUG

set to some value to have it output logging details of how it is performing its search.

py -3.6

(specific version)

Search
```
PATH
```
for
```
python3.6
```

py -3

(loose/major version)

Check for the
```
PY_PYTHON3
```
environment variable, and if defined and not the empty string then use it as the specific version (e.g.
```
PY_PYTHON3=3.6
```
)
Search
```
PATH
```
for all instances of
```
python3.*
```
Find the executable with the newest version number that comes earliest on
```
PATH
```

py

(any version)

Use
```
${VIRTUAL_ENV}/bin/python
```
immediately if available
Use
```
.venv/bin/python
```
immediately if available
If the first argument is a file path ...
1. Check for a shebang
2. If shebang path starts with
```
/usr/bin/python
```
  ,
```
/usr/local/bin/python
```
  ,
```
/usr/bin/env python
```
  or
```
python
```
  , proceed based on the version found on that path (bare
```
python
```
  is considered the equivalent of not specifying a Python version)
Check for the
```
PY_PYTHON
```
environment variable, and if defined then use it as the loose or specific version (e.g.
```
PY_PYTHON=3
```
or
```
PY_PYTHON=3.6
```
)
Search
```
PATH
```
for all instances of
```
python*.*
```
Find the executable with the newest version that is earliest on
```
PATH
```

TODO

Issues to finish to reach MVP

Appendix

PEP 397: Python launcher for Windows
PEP 486: Make the Python Launcher aware of virtual environments
Windows Launcher
- Documentation
- Source