averages.py

import collections
import random


class RollingAverage:
    """Generates a function that tracks a rolling average of a given size."""
    def __init__(self, size):
        self.size = size
        self.deque = collections.deque(list(), self.size)
        self.count = 0

    def __call__(self, value):
        """Returns the average of the previous self.size values."""
        self.deque.append(value)
        self.count += 1
        if self.count < self.size:
            return None
        return sum(self.deque) / float(self.size)


def main():
    """Passes 50 random integers to a RollingAverage obj tracking 5 values."""
    five = RollingAverage(5)
    for i in xrange(50):
        value = random.randrange(0, 100)
        print 'five(%s) = %s    %s' % (str(value).rjust(2), five(value), five.deque)

if __name__ == '__main__':
    main()

sample_output.txt

five(14) = None    deque([14], maxlen=5)
five(93) = None    deque([14, 93], maxlen=5)
five(69) = None    deque([14, 93, 69], maxlen=5)
five(64) = None    deque([14, 93, 69, 64], maxlen=5)
five(50) = 58.0    deque([14, 93, 69, 64, 50], maxlen=5)
five(99) = 75.0    deque([93, 69, 64, 50, 99], maxlen=5)
five(78) = 72.0    deque([69, 64, 50, 99, 78], maxlen=5)
five(89) = 76.0    deque([64, 50, 99, 78, 89], maxlen=5)
five( 2) = 63.6    deque([50, 99, 78, 89, 2], maxlen=5)
five(30) = 59.6    deque([99, 78, 89, 2, 30], maxlen=5)
five(44) = 48.6    deque([78, 89, 2, 30, 44], maxlen=5)
five(54) = 43.8    deque([89, 2, 30, 44, 54], maxlen=5)
five(12) = 28.4    deque([2, 30, 44, 54, 12], maxlen=5)
five(39) = 35.8    deque([30, 44, 54, 12, 39], maxlen=5)
five(61) = 42.0    deque([44, 54, 12, 39, 61], maxlen=5)
five(44) = 42.0    deque([54, 12, 39, 61, 44], maxlen=5)
five(31) = 37.4    deque([12, 39, 61, 44, 31], maxlen=5)
five(41) = 43.2    deque([39, 61, 44, 31, 41], maxlen=5)
five(88) = 53.0    deque([61, 44, 31, 41, 88], maxlen=5)
five(49) = 50.6    deque([44, 31, 41, 88, 49], maxlen=5)
five(73) = 56.4    deque([31, 41, 88, 49, 73], maxlen=5)
five(51) = 60.4    deque([41, 88, 49, 73, 51], maxlen=5)
five(57) = 63.6    deque([88, 49, 73, 51, 57], maxlen=5)
five(24) = 50.8    deque([49, 73, 51, 57, 24], maxlen=5)
five(10) = 43.0    deque([73, 51, 57, 24, 10], maxlen=5)
five(70) = 42.4    deque([51, 57, 24, 10, 70], maxlen=5)
five( 7) = 33.6    deque([57, 24, 10, 70, 7], maxlen=5)
five(91) = 40.4    deque([24, 10, 70, 7, 91], maxlen=5)
five(59) = 47.4    deque([10, 70, 7, 91, 59], maxlen=5)
five(17) = 48.8    deque([70, 7, 91, 59, 17], maxlen=5)
five(53) = 45.4    deque([7, 91, 59, 17, 53], maxlen=5)
five(12) = 46.4    deque([91, 59, 17, 53, 12], maxlen=5)
five(84) = 45.0    deque([59, 17, 53, 12, 84], maxlen=5)
five( 7) = 34.6    deque([17, 53, 12, 84, 7], maxlen=5)
five(79) = 47.0    deque([53, 12, 84, 7, 79], maxlen=5)
five(92) = 54.8    deque([12, 84, 7, 79, 92], maxlen=5)
five(27) = 57.8    deque([84, 7, 79, 92, 27], maxlen=5)
five(34) = 47.8    deque([7, 79, 92, 27, 34], maxlen=5)
five(63) = 59.0    deque([79, 92, 27, 34, 63], maxlen=5)
five(91) = 61.4    deque([92, 27, 34, 63, 91], maxlen=5)
five(47) = 52.4    deque([27, 34, 63, 91, 47], maxlen=5)
five(98) = 66.6    deque([34, 63, 91, 47, 98], maxlen=5)
five(70) = 73.8    deque([63, 91, 47, 98, 70], maxlen=5)
five(95) = 80.2    deque([91, 47, 98, 70, 95], maxlen=5)
five(92) = 80.4    deque([47, 98, 70, 95, 92], maxlen=5)
five(98) = 90.6    deque([98, 70, 95, 92, 98], maxlen=5)
five(50) = 81.0    deque([70, 95, 92, 98, 50], maxlen=5)
five(93) = 85.6    deque([95, 92, 98, 50, 93], maxlen=5)
five(34) = 73.4    deque([92, 98, 50, 93, 34], maxlen=5)
five(95) = 74.0    deque([98, 50, 93, 34, 95], maxlen=5)