In [25]:
def my_mean(input_list):
    sum_list = 0
    count_list = 0
    
    for i in input_list:
        sum_list += i
        count_list += 1
    
    return sum_list/count_list

In [29]:
input_list = [1,2,3,4,5,6,7,8]
my_mean(input_list)


Out[29]:
4.5