macro-polo 0.3.0

Rust-style macros for Python

Explore new syntax!

macro-polo brings Rust-inspired compile-time macros to Python. It’s currently in very early alpha, but even if it ever gets a stable release, you probably shouldn’t use it in any serious project. Even if you find a legitimate use case, the complete lack of tooling support almost definitely outweighs the benefits. That said, if you do decide to use it, I’d love to know why!

Installation

pip install macro-polo

Usage

macro-polo is modular, and can be extended at multiple levels. See the API Reference for more details.

The simplest way to use it is to add a coding: macro-polo comment to the top of your source file (in one of the first two lines). You can then declare and invoke macros using the macro_rules! syntax.

Example (examples/macro_rules/bijection.py):

# coding: macro-polo
"""A basic demonstration of `macro_rules!`."""


macro_rules! bijection:
    [$($key:tt: $val:tt),* $(,)?]:
        (
            {$($key: $val),*},
            {$($val: $key),*}
        )


macro_rules! debug_print:
    [$($expr:tt)*]:
        print(
            stringify!($($expr)*), '=>', repr($($expr)*),
            file=__import__('sys').stderr,
        )


names_to_colors, colors_to_names = bijection! {
    'red': (1, 0, 0),
    'green': (0, 1, 0),
    'blue': (0, 0, 1),
}


debug_print!(names_to_colors)
debug_print!(colors_to_names)

debug_print!(names_to_colors['green'])
debug_print!(colors_to_names[(0, 0, 1)])

$ python3 examples/bijection.py
names_to_colors  => {'red': (1, 0, 0), 'green': (0, 1, 0), 'blue': (0, 0, 1)}
colors_to_names  => {(1, 0, 0): 'red', (0, 1, 0): 'green', (0, 0, 1): 'blue'}
names_to_colors ['green'] => (0, 1, 0)
colors_to_names [(0 ,0 ,1 )] => 'blue'

Viewing the generated code:

$ python3 -m macro_polo examples/bijection.py | ruff format -

names_to_colors, colors_to_names = (
    {'red': (1, 0, 0), 'green': (0, 1, 0), 'blue': (0, 0, 1)},
    {(1, 0, 0): 'red', (0, 1, 0): 'green', (0, 0, 1): 'blue'},
)
print(
    'names_to_colors',
    '=>',
    repr(names_to_colors),
    file=__import__('sys').stderr,
)
print(
    'colors_to_names',
    '=>',
    repr(colors_to_names),
    file=__import__('sys').stderr,
)
print(
    "names_to_colors ['green']",
    '=>',
    repr(names_to_colors['green']),
    file=__import__('sys').stderr,
)
print(
    'colors_to_names [(0 ,0 ,1 )]',
    '=>',
    repr(colors_to_names[(0, 0, 1)]),
    file=__import__('sys').stderr,
)

Interested?

Check out the full documentation and tutorial.