import sys
list1=[]

count1=0
for line in sys.stdin:
    i = float(line.rstrip())
    if(i<0):
        count1+=1
    else:
        list1.append(i)
print(count1)
num = len(list1)
if num == 0:
    print(round(0,1))
else:
    print(round(sum(list1)/num,1))

平均数用内置函数这样求：sum(list1)/len(list1),

调包这样求：

import statistics

my_list = [1, 2, 3, 4, 5]

average = statistics.mean(my_list)

print(average) # 输出：3.0