IO monad, naïve implementation

io1.py

class IO:
    def __init__(self, action, arg):
        self.action = action
        self.arg = arg

    def __rshift__(self, func):  # this is "bind" (>>)
        if self.action == "getLine":
            line = input()
            return func(line)
        elif self.action == "putStrLn":
            print(self.arg)      # always returns None
            return func(None)
        elif self.action == "return":
            return func(self.arg)
        else:
            raise RuntimeError("oops")

    @staticmethod
    def unit(v):
        return IO("return", v)

def putStrLn(text):
    return IO("putStrLn", text)

getLine = IO("getLine", None)

main = (
    putStrLn("What's your name?") >> (lambda _:
        getLine >> (lambda name:
            putStrLn("Hello " + name)
        )
    )
)

main >> (lambda _: IO.unit(None))