factory.py

#!/usr/bin/env python3
from abc import ABC, abstractmethod
from dataclasses import dataclass


class Writer(ABC):
    @abstractmethod
    def write(self, text: str) -> None:
        pass


class XML(Writer):
    def write(self, text: str) -> None:
        print('YEAH du XML !!')
        print(text)


class CSV(Writer):
    def write(self, text: str) -> None:
        print('AAAH du CSV !!')
        print(text)


@dataclass
class Config:
    output_fmt: str = 'xml'


class Factory:
    @classmethod
    def init(cls, output_fmt: str) -> Writer:
        if output_fmt == 'xml':
            output: Writer = XML()
        elif output_fmt == 'csv':
            output: Writer = CSV()
        return output


class App:
    def __init__(self, config: Config = Config()) -> None:
        self.output: Writer = Factory.init(config.output_fmt)

    def hello(self) -> None:
        self.output.write('hello world')


class T(Writer):
    pass


def main() -> None:
    app: App = App()
    app.hello()
    app = App(Config('csv'))
    app.hello()
    t: T = T()


if __name__ == '__main__':
    main()