functions_factory.py

from typing import Any
from dataclasses import dataclass


class FunctionType:
    const = 'const'
    call = 'call'


@dataclass
class FunctionSpec:
    name: str
    type: str
    body: Any


class Function:
    def __init__(self, spec: FunctionSpec):
        self.spec = spec

    def __call__(self, *args):
        if self.spec.type == FunctionType.const:
            return self.spec.body
        elif self.spec.type == FunctionType.call:
            obj, *other = args
            return getattr(obj, self.spec.body).__call__(*other)
        else:
            raise ValueError(f"Bad function type `{self.spec.type}`")


class FunctionsFactory:
    """ Builds functions by provided specs """

    def __init__(self, spec: list[FunctionSpec]):
        self._spec = spec
        self._functions: dict[str, Function] = dict()

        self._generate()

    def _generate(self):
        for i in self._spec:
            self._functions.update({i.name: Function(i)})

    def __getattr__(self, item) -> Function:
        if item in self._functions:
            return self._functions[item]
        else:
            return self.__getattribute__(item)


def main():

    commands = [
        {'name': 'zero', 'type': 'const', 'body': 0},
        {'name': 'one', 'type': 'const', 'body': 1},
        {'name': 'two', 'type': 'const', 'body': 2},
        {'name': 'three', 'type': 'const', 'body': 3},
        {'name': 'four', 'type': 'const', 'body': 4},
        {'name': 'five', 'type': 'const', 'body': 5},
        {'name': 'six', 'type': 'const', 'body': 6},
        {'name': 'seven', 'type': 'const', 'body': 7},
        {'name': 'eight', 'type': 'const', 'body': 8},
        {'name': 'nine', 'type': 'const', 'body': 9},
        {'name': 'add', 'type': 'call', 'body': '__add__'},
        {'name': 'mul', 'type': 'call', 'body': '__mul__'},
        {'name': 'sub', 'type': 'call', 'body': '__sub__'},
        {'name': 'div', 'type': 'call', 'body': '__truediv__'},
    ]

    factory = FunctionsFactory([FunctionSpec(**data) for data in commands])
    f = factory

    print(
        f.mul(f.add(f.one(), f.two()), f.two())  # 6
    )


if __name__ == '__main__':
    main()