python中文本文件的切片和切分

Question

我正在编写一段代码，其中我想从mbox.text文件中搜索术语“X置信度: 0.8475”。到目前为止，我可以搜索字符串并计数它在文件中出现的次数。现在的问题是，每次该字符串出现在文本文件中时，我都必须添加该字符串(此处- 0.8475 )的末尾数字。我需要帮助，因为我停留在那里，无法计算出现在字符串末尾的浮点数的总数。

我的文件内容如下：

X-Content-Type-Message-Body: text/plain; charset=UTF-8
Content-Type: text/plain; charset=UTF-8
X-DSPAM-Result: Innocent
X-DSPAM-Processed: Sat Jan  5 09:14:16 2008
X-DSPAM-Confidence: 0.8475
X-DSPAM-Probability: 0.0000

我的代码：

text_file = raw_input ("please enter the path of the file that you want to          open:")
open_file = open ( text_file )
print "Text file has been open " 
count = 0
total = 0.00000
for line in open_file:
    if 'X-DSPAM-Confidence:' in line:
        total =+ float(line[20:])
        count = count + 1
print total/count
print "The number of line with X-DSPAM-Confidence: is:", count

我怎么能这么做？

Answer 1

切片返回的是一个列表，而不是一个值，添加的原位操作符是+=而不是=+。也就是说，你应该使用split。

total = 0.00000
for line in open_file:
    if 'X-DSPAM-Confidence:' in line:
        total += float(line.split()[-1]) # change here.
        count = count + 1
print total/count

或者更好地使用sum和len。

with open('test.txt') as f:
    data = [float(line.split()[-1]) for line in f if line.strip().startswith('X-DSPAM-Confidence:')]
    print(sum(data)/len(data))

Python3.4或更高版本的解决方案使用来自mean模块的statistics。

from statistics import mean


with open('test.txt') as f:
    data = [float(line.split()[-1]) for line in f if line.strip().startswith('X-DSPAM-Confidence:')]
    print(mean(data))

Answer 2

print语句，就像一个神奇的8-Ball，告诉了所有人。

>>> print repr(line[20:])
' 0.0000\n'

你只需比float所能选择的更多。把它缩小一点

total += float(line[21:-1])