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Task/Standard-deviation/Python/standard-deviation-4.py

@@ -0,0 +1,24 @@
+>>> from math import sqrt
+>>> def sdcreator():
+	sum = sum2 = n = 0
+	while True:
+		x = yield sqrt(sum2/n - sum*sum/n/n) if n else None
+
+		sum  += x
+		sum2 += x*x
+		n    += 1.0
+
+>>> sd = sdcreator()
+>>> sd.send(None)
+>>> for value in (2,4,4,4,5,5,7,9):
+	print (value, sd.send(value))
+
+	
+2 0.0
+4 1.0
+4 0.942809041582
+4 0.866025403784
+5 0.979795897113
+5 1.0
+7 1.39970842445
+9 2.0