Maybe Monad in Python 3

maybe_monad.py

#!/usr/bin/env python3
import functools
from typing import TypeVar, Generic, Callable, Optional

T = TypeVar('T')


class Maybe(Generic[T]):
    def __init__(self, value: T) -> None:
        self.value = value

    def __repr__(self) -> str:
        return f"Maybe({self.value})"

    def get(self) -> T:
        return self.value


def with_maybe(transform: Callable[[T], T]) -> Callable:
    @functools.wraps(transform)
    def wrapper(input_: Maybe[T]) -> Maybe[T]:
        if input_.value is None:
            return Maybe(None)
        return Maybe(transform(input_.value))
    return wrapper


@with_maybe
def add_one(x: int) -> int:
    return x + 1


@with_maybe
def multiply_by_two(x: int) -> int:
    return x * 2


n0: str = input("Please enter an integer: ")
print(f"n0 = '{n0}'")
n0_ = None if n0 == "" else int(n0)
n1: Maybe[Optional[int]] = Maybe(n0_)
print(f"n1 = {n1}")
n2: Maybe[Optional[int]] = add_one(n1)
print(f"n2 = {n2}")
n3: Maybe[Optional[int]] = multiply_by_two(n2)
print(n3.value)