从 txt 文件的多行中提取某些值

Question

Similar questions have been asked and answered before, but I'd like to know why my code doesn't yield the correct output.

There are a couple of lines in my txt file that look like this: X-DSPAM-Confidence: 0.xxxx

The 0.xxxx value varies. I need to slice that part out of each "X-DSPAM-Confidence:" line and calculate an average.

The txt file can be downloaded here: http://www.py4e.com/code3/mbox-short.txt

My code is as follows:

fname = input("Enter file name: ")
fh = open(fname)
count = 0
current = 0
for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") : continue   # Please do not change this line and develop the program based on it
    count = count + 1  # I think this would count how many lines that starts with X-DSPAM-Confidence:
    pos = line.find(':')    # This should find me the position for ":"
    number = line[pos+5:]   # I think this should slice the number out
    final = float(number) + current    # Then I float the number and add to the current running number
print("Average spam confidence: ", final/count)    # Finally, when the loop finishes with the file, print the average

Using the code above, I got the average 33.5925925926, but the correct answer should be 0.750718518519.

Can someone please enlighten me?

Answer 1

As you requested, with minimal but essential changes.

    fname = input("Enter file name: ")
    with open(fname, "r") as current_file: 
        # i can not stress enough the importance of the with method over 
        #open()/close()
            content = current_file.readlines()

    count = 0
    current = 0
    for line in content:
        if not line.startswith("X-DSPAM-Confidence:"): continue
        count = count + 1  
        pos = line.find(':')    
        number = line[pos+2:]   # small error, it was not 5 but 2 instead
        current = float(number) + current
    print("Average spam confidence: ", current/count)