Improve n period Sharpe Ratio indicator

[Sumit Pandey]

Hi,
I have written a code to calculate the sharpe ratio of security.

class sharpe(bt.Indicator):
    lines = ('sharpe',)
    params=dict(period=151)

    def __init__(self):
        self.addminperiod(self.p.period)
        #self.roc= self.data(-1) / self.data(-self.p.period) - 1.0
        #self.stdev=bt.ind.StdDev(self.data,period=self.p.period)
        #self.lines.sharpe=self.roc/self.stdev
    def next(self):
        iterdata = self.data.get(size=self.p.period+1)
        returns= [a1 / a2 - 1 for a1, a2 in zip(iterdata[1:], iterdata)]
        avgret= np.average(returns)
        stdev=np.std(returns)
        self.lines.sharpe[0] = (avgret/stdev)

Here I have taken Rf to be zero.
Can someone optimize this code (write a better version) if possible?