posmatch 0.4.0

Positional subpattern matching for custom classes.

Positional subpattern matching for custom classes.

Note: This is mostly a toy project. Using it will save you one line of boiler-plate code at the cost of an additional decorator or argument. In many cases, the same effect can be easily achieved by using a dataclass.

Requirements

Python 3.8 or higher.

Note: Although this package itself does not require Python 3.10, its usage only makes sense with the new pattern matching feature introduced in Python 3.10.

Installation

pip install posmatch

Usage

The pos_match decorator

from posmatch import pos_match

@pos_match
class Color:

    def __init__(self, r, g, b):
        self.r = r
        self.g = g
        self.b = b


color = Color(64, 64, 64)

match color:
    case Color(0, 0, b):
        print('shade of blue')
    case Color(r, g, b) if r == g == b:
        print('shade of grey')
    case _:
        print('other color')

Output:

shade of grey

The PosMatchMeta metaclass

from posmatch import PosMatchMeta


class Color(metaclass=PosMatchMeta):

    def __init__(self, r, g, b):
        self.r = r
        self.g = g
        self.b = b


color = Color(0, 0, 64)

match color:
    case Color(0, 0, b):
        print('shade of blue')
    case Color(r, g, b) if r == g == b:
        print('shade of grey')
    case _:
        print('other color')

Output:

shade of blue