python 闭包计算移动均值及nonlocal的使用

class Averager1():
    '''计算移动平均值的类第一种写法'''
    def __init__(self):
        self.series = []

    def __call__(self,new_value):
        self.series.append(new_value)
        total = sum(self.series)
        return total/len(self.series)

# avg1 = Averager1()
# print(avg1(10))
# print(avg1(11))
# print(avg1(12))

def make_averager():
    '''计算移动平均值的类第二种写法（闭包）'''
    series = [] #自由变量，历史数据保存在avg1.__closure__[0].cell_contents 中
    def averager(new_value):
        series.append(new_value)
        total = sum(series)
        return total/len(series)
    return averager

avg1 = make_averager()
print(avg1(10))
print(avg1(11))
print(avg1(12))

def make_averager1():
    '''计算移动平均值的类第三种写法（nonlocal）不保存所有历史，提高效率'''
    count = 0
    total = 0
    def averager(new_value):
        nonlocal count,total #把变量标记为自由变量，不会因为不可变类型而变成局部变量而不保存在闭包中
        count +=1
        total += new_value
        return total/count
    return averager

avg1 = make_averager1()
print(avg1(10))
print(avg1(11))
print(avg1(12))