10-minute option.py hack

option.py

class Option:
    def __init__(self, *args):
        if len(args) == 0:
            self._tag = "None"
            self._value = None
        elif len(args) == 1:
            self._tag = "Some"
            self._value = args[0]
        else:
            raise RuntimeError("Invalid arity")

    @staticmethod
    def some(value):
        return Option(value)

    @staticmethod
    def none():
        return Option()

    def is_some(self) -> bool:
        return self._tag == "Some"

    def is_none(self) -> bool:
        return self._tag == "None"

    def map(self, f):
        if self._tag == "Some":
            return Option(f(self._value))
        else:
            return self

    def unwrap(self):
        if self._tag == "Some":
            return self._value
        else:
            raise RuntimeError("unwrap")

    def unwrap_or(self, default_value):
        if self._tag == "Some":
            return self._value
        else:
            return default_value

    def unwrap_or_else(self, f):
        if self._tag == "Some":
            return self._value
        else:
            return f()

    def or_(self, optb):
        if self.is_some():
            return self
        else:
            return optb

    def or_else(self, f):
        if self.is_some():
            return self
        else:
            return f()

    def and_(self, optb):
        if self.is_none():
            return self
        else:
            return optb

    def and_then(self, f):
        if self.is_none():
            return self
        else:
            return f(self.unwrap())


opt = Option(1).map(lambda x: x + 1).and_then(lambda x: Option.none()).or_(Option(4))

print(opt.unwrap_or_else(lambda: 4))