对列表中的浮点数求和

Question

我有一份从文件中取出的数字清单。

fh = open(<filename>)
for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") : continue
    num = float(line[20 : ])
    print(num)

输出：

0.6178
0.6961000000000001
0.7565
0.7625999999999999
0.7556
0.7002
0.7615

我必须将它们相加，然后取平均值(“我不能使用sum()")。我试着用'for‘遍历它们，然后用/操作符求和并得到平均值；但我得到了以下错误'float’object is not iterable。

我尝试了：

fh = open(<filename>)
for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") : continue
    num = float(line[20 : ])
    for n in num: 
        n = n + n  
    print(n)

有了这个，'float‘对象的错误是不可迭代的。

此外，我也尝试将数字添加到数组中，看看是否可以在数组中循环，但这对我也不起作用。

Answer 1

您需要将总和累加到行上的for循环中的一个变量中。您还必须计算行数。你可以在你的代码中这样做：

fh = open(<filename>)
sum_num = 0 # Initialize the sum to 0
count = 0 # Initialize the counter of lines to 0
for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") : continue
    num = float(line[20 : ])
    sum_num += num # Add your number to the sum
    count += 1 # Add 1 to your counter of lines
    print(num)

print(sum_num) # Print the sum
print(sum_num/count) # Print average which is just the sum divided by the number of lines

Answer 2

我认为你需要一个循环外的变量，例如：

fh = open(<filename>)

numbers = []
for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") : continue
    num = float(line[20 : ])
    # save num into a list for later use
    numbers.append(num)

# perform calculations 
total = 0
for num in numbers:
    total += num
average = total / len(numbers)

代码的问题是num是一个float，您不能遍历它。

Answer 3

这是一个简单的解决方案

fh = open(<filename>)
total = 0 
for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") : continue
    num = float(line[20 : ])
    total += n 
print(total)