不需任何外庫
#樣本標準差
def stdDeviation(a):
l=len(a)
m=sum(a)/l
d=0
for i in a: d+=(i-m)**2
return (d*(1/l))**0.5
a=[5,6,8,9]
print(stdDeviation(a))
========
1.5811388300841898