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))