Ngrams with coroutines

gistfile1.py

def coroutine(func):
    """ A decorator function that takes care 
    of starting a coroutine automatically on call """
    def start(*args,**kwargs):
        coro = func(*args,**kwargs)
        coro.next()
        return coro
    return start

@coroutine
def ngrams(n, target):
    """ A coroutine to generate ngrams. 
    Accepts one char at a time """
    chars = collections.deque()
    while True:
        chars.append((yield))
        if len(chars) == n: 
            target.send(chars)
            chars.popleft()