python类型错误：无效类型不支持索引

Question

I am writing a program that finds a certain type of line from a file and finds numbers inside them and calculates their average.

Here it is:

total = 0    
count = 0

fname = raw_input("Enter file name: ")    
fh = open(fname)

for line in fh:    
    if line.startswith('X-DSPAM-Confidence:'):

        count = float(count) + 1    
        x = fh[22:29]

        total = float(total) + float(x)

    else: 
        continue

print total/count

I get:

TypeError: '<Invalid Type>' does not support indexing on line 8.

Answer 1

I'll extend on my comment.

Your code (limited to your issue) is:

fh = open(fname)
for line in fh:
    x = fh[22:29]

fh is actually a file object, which does not support slice syntax. If you want to retrieve information from line you have to actually perform operation on line.

fh = open(fname)
for line in fh:
    x = line[22:29]

Answer 2

You're looking at the file and not the line. Also, you should simplify your code.

total = 0.0
count = 0.0
# Headers look like this:
# X-DSPAM-Confidence: 0.9928
dspam_header = 'X-DSPAM-Confidence:'
fname = raw_input("Enter file name: ")
with open(fname) as fh:
    for line in fh:
        if not line.startswith(dspam_header):
            continue

        count += 1
        total += float(line[len(dspam_header):])

if count:
    print total/count