L = [75, 92, 59, 68, 99]

def avg(l):

    return sum(l) / len(l)

def avg2(l):

    sum1 = 0

    for i in  l:

        sum1 += i

    return sum1 / len(l)

average = avg2(L)

print(average)

L = [75, 92, 59, 68, 99]

def avg(l):

    return sum(l) / len(l)

def avg2(l):

    sum1 = 0

    for i in  l:

        sum1 += i

    return sum1 / len(l)

average = avg2(L)

print(average)

这是累加

sum = sum + x的意思是将sum + x的结果再赋值给sum,也就是sum = 0 + 75 = 75

下次计算时, sum的取值是75而不是0