IO monad recreated in Python

pure-io.py

class IO(object):
    @classmethod
    def ret(cls, x):
        return IOReturn(x)

    def bind(self, f):
        return IOBind(self, f)


class IOBind(IO):
    def __init__(self, bindm, bindf):
        self.bindm = bindm
        self.bindf = bindf


class IOReturn(IO):
    def __init__(self, x):
        self.x = x


class IOPrint(IO):
    def __init__(self, str_):
        self.op = 'print'
        self.str = str_


class IORead(IO):
    def __init__(self):
        self.op = 'read'


ioprint = lambda str_: IOPrint(str_)
ioread = lambda: IORead()

def runIO(io):
    if hasattr(io, 'bindm') and hasattr(io, 'bindf'):
        x = runIO(io.bindm)
        return runIO(io.bindf(x))
    if hasattr(io, 'x'):
        return io.x
    if getattr(io, 'op') == 'print':
        print io.str
        return ()
    if getattr(io, 'op') == 'read':
        return raw_input()


#
# Example program
#

import re

getname = (lambda:
    ioprint('what is your name?').bind(lambda _:
    ioread().bind(lambda name:
    IO.ret(name) if re.match('^[A-Z][a-z]+$', name) else
    getname()
)))

main = (lambda:
    getname().bind(lambda name:
    ioprint('Hello, ' + name)
))


runIO(main())