spacepaste

from greenlet import greenlet

# -------------- begin support code

class genlet(greenlet):

    def __init__(self, *args, **kwds):
        self.args = args
        self.kwds = kwds

    def run(self):
        fn, = self.fn
        fn(*self.args, **self.kwds)

    def __iter__(self):
        return self

    def __next__(self):
        self.parent = greenlet.getcurrent()
        result = self.switch()
        if self:
            return result
        else:
            raise StopIteration

    # Hack: Python < 2.6 compatibility
    next = __next__

    @classmethod
    def _getgenlet(cls):
        g = greenlet.getcurrent()
        while not isinstance(g, cls):
            if g is None:
                raise RuntimeError('yield outside a genlet')
            g = g.parent
        return g

def Yield(value):
    genlet._getgenlet().parent.switch(value)

def YieldFrom(gen):
    g = genlet._getgenlet()
    for value in gen:
        g.parent.switch(value)

def generator(func):
    class generator(genlet):
        fn = (func,)
    return generator

# -------------- end support code

if __name__ == "__main__":

    @generator
    def g(n):
        for i in range(n):
            Yield(i)

    @generator
    def f():
        YieldFrom(g(5))

    # direct use of a generator
    for i in g(5):
        print i

    # using a generator that forwards from another
    for i in f():
        print i