A generator for incremental averaging in Python

average.py

def consumer(func):
    """
    See: http://www.dabeaz.com/generators/
    """
    def start(*args,**kwargs):
        c = func(*args,**kwargs)
        c.next()
        return c
    return start

@consumer
def incavg(val = None):
    """
    Can optionally send the first value at initialization. 
    """

    cnt = 0
    avg = 0
    
    if not val is None:
        cnt = 1
        avg = val

    while True:
        val = (yield avg)

        if val is None:
            pass # next was called
        elif cnt == 0: # first value
            cnt = 1
            avg = val
        else:
            cnt += 1
            avg = avg + (val - avg) / float(cnt)