在python中不使用sum函数的平均计算?

我正在尝试解出一个用于读取文本文件的python代码,然后选择一些类似的文本,然后从中收集浮点数并计算其平均值, 不使用SUM功能 .

但我有一列列表,列出了每个数字的平均值及其前面的数字!最后一个是我的答案,但我无法选择最后一个字符,因为蟒蛇将其视为一列奇怪的数字!

这是我的代码:

count = 0
total = 0

while True:   
    inp = raw_input ("Enter file name: ")
    if inp == 'myfile.txt' : break

fh = open(inp)
for line in fh:
    line = line.rstrip()
    if line.startswith("my_pattern") :
        count = count + 1
        sb = line.split()
        sc = sb[1]    # this gaves me the numbers only from eavh line #
        value = float(sc)

        total = total + value
        average = total/count
        print average

答案是:

0.8475     (*this is exactly the first number, I mean it is the average of just one number, Itself !*)
0.73265     (*this is the average of two numbers, the second number and the number 0.8475*)
0.728447368421
0.727035
0.728385714286
0.726895454545
0.725547826087
0.7268
0.737112     (this is the answer, but I do not want a column of numbers and by the way, I could not split just this number)