Handy script for calculating averages streamed via stdin

runningavg.py

#!/usr/bin/env python
import sys
import math

CHUNK = 100

if len(sys.argv) > 1:
    CHUNK = int(sys.argv[1])

s = 0
ss = 0
n = 0
i = 1
while 1:
    l = sys.stdin.readline()
    if not l:
        break
    num = float(l.strip())
    s += num
    ss += (num * num)
    n += 1
    if i % CHUNK == 0:
        m = s / n
        print "Count: %10d - Total: %10.4f - Average: %10.4f - Std Dev: %10.4f" % (
            n, s, m, math.sqrt((ss / n) - (m * m)) )
    i += 1

m = s / n
print "Count: %10d - Total: %10.4f - Average: %10.4f - Std Dev: %10.4f" % (
    n, s, m, math.sqrt((ss / n) - (m * m)))