all tasks

Task/Standard-deviation/Python/standard-deviation-1.py

@@ -0,0 +1,22 @@
+>>> from math import sqrt
+>>> def sd(x):
+    sd.sum  += x
+    sd.sum2 += x*x
+    sd.n    += 1.0
+    sum, sum2, n = sd.sum, sd.sum2, sd.n
+    return sqrt(sum2/n - sum*sum/n/n)
+
+>>> sd.sum = sd.sum2 = sd.n = 0
+>>> for value in (2,4,4,4,5,5,7,9):
+    print (value, sd(value))
+
+
+(2, 0.0)
+(4, 1.0)
+(4, 0.94280904158206258)
+(4, 0.8660254037844386)
+(5, 0.97979589711327075)
+(5, 1.0)
+(7, 1.3997084244475311)
+(9, 2.0)
+>>>

Task/Standard-deviation/Python/standard-deviation-2.py

@@ -0,0 +1,13 @@
+>>> class SD(object): # Plain () for python 3.x
+	def __init__(self):
+		self.sum, self.sum2, self.n = (0,0,0)
+	def sd(self, x):
+		self.sum  += x
+		self.sum2 += x*x
+		self.n    += 1.0
+		sum, sum2, n = self.sum, self.sum2, self.n
+		return sqrt(sum2/n - sum*sum/n/n)
+
+>>> sd_inst = SD()
+>>> for value in (2,4,4,4,5,5,7,9):
+	print (value, sd_inst.sd(value))

Task/Standard-deviation/Python/standard-deviation-3.py

@@ -0,0 +1,25 @@
+>>> from math import sqrt
+>>> def sdcreator():
+	sum = sum2 = n = 0
+	def sd(x):
+		nonlocal sum, sum2, n
+
+		sum  += x
+		sum2 += x*x
+		n    += 1.0
+		return sqrt(sum2/n - sum*sum/n/n)
+	return sd
+
+>>> sd = sdcreator()
+>>> for value in (2,4,4,4,5,5,7,9):
+	print (value, sd(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

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