从键盘输入一个列表，计算输出列表元素的均方差。请参照代码模板，完善代码。①s = 0.0for num in numlist:s = s + numreturn s/len(numlist)def dev(numlist,②):sdev = 0.0for num in numlist:sdev = sdev + (num - average)**2return (sdev /(len(numlist)-1) )** 0.5#返回均方差#请输入一个列表：ls = eval(input(""))avg=mean(ls)print("均方差为：{:.2f}".format(③))