Online mean and variance with generators

stats_coroutines.py

def online_mean():
    """
    Return an initialised generator for online mean (next() has been called).
    """
    omean = _online_mean()
    next(omean)
    return omean


def _online_mean():
    n = 0
    mean = 0
    while(True):
        if (n < 1):
            x = yield 0
        else:
            x = yield mean
        n = n + 1
        delta = x - mean
        mean = mean + delta/n
        
        
def online_variance():
    """
    Return an initialised generator for online variance (next() has been called).
    """
    ovar = _online_variance()
    next(ovar)
    return ovar


def _online_variance():
    n = 0
    mean = 0
    M2 = 0
    while(True):
        if (n < 2):
            x = yield 0
        else:
            x = yield M2/(n - 1)
        n = n + 1
        delta = x - mean
        mean = mean + delta/n
        M2 = M2 + delta*(x - mean)
        
        
omean = online_mean()
ommean = online_moving_mean()
ovar = online_variance()
for x in range(100):
    print(x, omean.send(x), ommean.send(x), ovar.send(x)**0.5)