converter.py

#!/usr/bin/env python3
from typing import Callable


class Converter:
    def __init__(self, lang: str = 'en') -> None:
        self.lang: str = lang
        if self.lang == 'fr':
            self.part: str = 'vers'
        elif self.lang == 'en':
            self.part = 'to'
        else:
            raise ValueError(f'Unknow lang "{self.lang}"')

    def add_conversion(self, orig: str, dest: str, rate: float) -> None:
        setattr(self, f'{orig}_{self.part}_{dest}',
                self._orig_to_dest(orig, dest, rate))
        setattr(self, f'{dest}_{self.part}_{orig}',
                self._orig_to_dest(orig, dest, rate, reverse=True))

    def _orig_to_dest(
        self, orig: str, dest: str, rate: float, reverse=False
    ) -> Callable:
        if not reverse:
            def from_to(from_: float) -> float:
                return from_ * rate
        else:
            def from_to(to: float) -> float:
                return to / rate
        return from_to


def main() -> None:
    c: Converter = Converter('en')
    c.add_conversion('euro', 'dollar', 1.12)
    c.add_conversion('euro', 'pound', .86)
    for attr in c.__dict__:
        if '_to_' in attr:
            print(f'{attr}: {getattr(c, attr)(1):.2f}')


if __name__ == '__main__':
    main()