This bit of code, uses the update funtion to calculate a dynamic running average that can be used for accurate analog sensing.

AnalogStats.py

class MovingStats:
    def __init__(self, alphaOrN):
        self.mean = 0
        self.var = 0
        self.started = False
        if (alphaOrN > 1):
            self.alpha = 2 / (alphaOrN - 1)
        else:
            self.alpha = alphaOrN

    def update(self, value):
        if (not self.started):
            self.mean = value
            self.var = 0
            self.started = True
        else:
            self.mean = self.mean - self.alpha * (self.mean - value);
            diff = value - self.mean
            self.var  = self.var - self.alpha * (self.var  - diff*diff);

    def normalize(self, value):
        stddev = math.sqrt(self.var)
        return ( value - self.mean ) / (stddev + 1e-10)

    def normalize01(self, value):
        norm = self.normalize(value)
        norm = norm / 6.0 + 0.5  # I'm actually not sure why this magical number 6 is here, maybe it has to be tested because this was made for the specific purpose of sensing heartbeats
        return norm