nonlocal

nonlocal 声明: 将变量标记为自由变量

def make_averager():    
    """计算移动平均值"""
    series = []    
    def averager(new_value):       
        # series 是自由变量：指未在本地作用域中绑定的变量 
        series.append(new_value)
        print(f'series : {series}')   
        total = sum(series)        
        return total/len(series)    
    return averager
avg = make_averager()
print(avg(10))
print(avg(11))
print(avg(12))
"""优化方案：
    只存储目前的总值和元素个数，然后使用这个两个数计算均值
nonlocal 声明: 将变量标记为自由变量
"""
def make_averager():
    """计算移动平均值 优化版本"""
    count = 0
    total = 0
    def averager(new_value):
        nonlocal count, total
        # 这里相当于隐形将count 变成了局部变量，引入nonlocal解决
        count += 1
        total += new_value
        return total / count
    return averager
avg2 = make_averager()
print(avg2(10))
print(avg2(11))
print(avg2(12))