如何用python计算基本统计值？

def getNum(): #从控制台获取多个不确定数据的方法
    nums = [];
    iNumStr = input("请输入数字(回车退出):");
    while iNumStr != "":
        nums.append(eval(iNumStr));
        iNumStr = input("请输入数字(回车退出):");
    return nums;
 
def mean(numbers):#计算平均值
    s = 0.0;
    for num in numbers:
        s = s + num;
    return s/len(numbers);
 
def dev(numbers, mean):#计算方差
    sdev = 0.0;
    for num in numbers:
        sdev = sdev + (num - mean)**2;
    return pow(sdev/(len(numbers)-1), 0.5);
 
def median(numbers):#计算中位数
    sorted(numbers);
    size = len(numbers);
    if size%2 == 0:
        med = (numbers[size//2-1] + numbers[size//2])/2;
    else:
        med = numbers[size//2];
    return med;
 
n = getNum();
m = mean(n);
 
print("平均值:{},方差:{:.2f},中位数:{}.".format(m, dev(n,m),median(n)));
 
#运行结果
#请输入数字(回车退出):10
#请输入数字(回车退出):20
#请输入数字(回车退出):30
#请输入数字(回车退出):
#平均值:20.0,方差:10.00,中位数:20.