Question

我是python的新手，我正在做这个练习我必须从文件中的特定行中提取数字。

任务是编写一个提示输入文件名的程序，然后打开该文件并读取文件，查找表单行： X-DSPAM-置信度：0.8475 对这些行进行计数并从每条线中提取浮点值，并计算这些值的平均值并生成输出，如下所示。您可以在下面测试时在http://www.pythonlearn.com/code/mbox-short.txt下载示例数据，输入mbox-short.txt作为文件名。

到目前为止，我还没有使用代码，我需要得到总数和计算来计算平均值：

http://i.gyazo.com/31373bdbc83c7f421236bc94d323d653.png

我应该得到这个平均结果： 0.750718518519

#Use the file name mbox-short.txt as the file name
fname = raw_input("Enter file name: ")
if len(fname) == 0:
    fname = 'file.txt'
fh = open(fname)
count = 0
total = 0
for line in fh:
    line = line.rstrip()
    if not line.startswith("For example    0.6545") : continue
    x = line[20:28]
    xx = float(x)
    count = count + 1

    print xx

    #average = total/count

    #print average

print "Done"

Answer 1

尝试一下： 从行中分离出float值后，如图所示列出它们，并使用for循环将这些值相加并计算平均值。代码：

fname = input("Enter file name:")
fh = open(fname)
count =0
number=[]
total=0
for line in fh:
    if not line.startswith("X-DSPAM-Confidence:"): 
        continue 
    #converting string to float  
    a=float(line[21:])
    #adding all the float values to a list
    number.append(a)    
    count =count+1
    total=0 
    #adding all the float values using a for loop
    for a in number: 
        total+=a     
        
avg = total/count
#to check if the numbers have been listed
print(number)
print(count)
print(total)
print("Average spam confidence:",avg)

Answer 2

试试这个：

# Using Regular Expressions
from re import match

fname = raw_input("Enter file name: ")
if len(fname) == 0:
    fname = 'file.txt'
fh = open(fname)
count = 0
total = 0.0
for line in fh:
    # Regular expression looks for "For example", followed by whitespace,
    # followed by digits (1 or more), with a decimal point, followed by digits (1 or more)
    # with some extra possible characters for whatever else (ignored)
    m = match('For example\s+(\d+\.\d+).*', line)
    if m: # If there was a match, m will have an instance (rather than None)
        # m.group(1) holds the float number string
        total += float(m.group(1))
        count += 1

fh.close()
print "Count:",count
print "Total:",total
print "Average:", total/count

Answer 3

编辑：哦，现在您已经在评论中posted the file了，并解释说您正在搜索数字，以＆＃34; X-DSPAM开头的行尾-Confidence：＆＃34;你要做的事情要清楚得多。这应该做你想要的。同样，一个避免正则表达式的简单解决方案。

答案是在python3中，但如果你正在使用python2，只需切换＆＃34;输入＆＃34; to＆＃34; raw_input＆＃34;并从print语句中删除括号。

file_name = input("Enter file name: ") # If you're using python2, replace "input" with "raw_input"

numbers = []
# Use with instead of manually opening and closing files. It's safer.
with open(file_name, encoding = "utf-8") as f:
    for line in f:
      if line.startswith("X-DSPAM-Confidence:"):
            # If the number is always the last thing in the line, we can split the
            # line on whitespace and grab the last item from the resulting list.
            # Then convert the string to a float and append it to our list of
            # numbers.
            number = float(line.split()[-1])
            numbers.append(number)

# Get the average by dividing the sum of the numbers by the length of the list.
average = sum(numbers) / len(numbers)
print(average) # If you're using python2, get rid of the parenthesis.

如果您对列表推导感到满意，那就更简单了：

file_name = input("Enter file name: ") # If you're using python2, replace "input" with "raw_input"

with open(file_name, encoding = "utf-8") as f:
    numbers = [float(line.split()[-1]) for line in f if line.startswith("X-DSPAM-Confidence:")]

average = sum(numbers) / len(numbers)
print(average) # If you're using python2, get rid of the parenthesis.

Answer 4

fname = raw_input("Enter File Name:")
count = 0
a = 0
try:
    fh = open(fname)
except:
    print 'file doesnt exist:', fname
    exit()

for line in fh:
    if not line.startswith("X-DSPAM-Confidence:"):continue
    print line

    colpos = line.find(':')


    number = float(line[colpos+1:])
    count = count + 1
    print number
    a = a + number


average = a / count
print 'average:',average

Answer 5

希望这段代码只需使用解析运算符

即可解决您的问题

U仍然可以使用find（）找到“：”的位置，并相应地更改切片运算符。

count = 0
total = 0`enter code here`
fname = raw_input("Enter file name: ")
fh = open(fname)
for line in fh:
    if line.startswith("X-DSPAM-Confidence:"):
        count = count+1
        total = total+float(line[20:26])
print "Average spam confidence:",total/count

Answer 6

你应该试试这个：

fh = open("mbox-short.txt",'r')

count=0
total=0
result=0

for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") :continue
    count=count+1
    num=float(line[21:])
    total=num+total

result=total/count
print("Average spam confidence:",result)

这是逻辑。了解三个变量num，count，total和result。它只是一个简单的代码！

Answer 7

cnt=0
total=0
final=0

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

for line in fh:
    if not line.startswith("X-DSPAM-Confidence:") : 
        continue
    cnt=cnt+1
    #print(line.strip())
    sm=float(line.split(":")[1])
    #print(sm)
    total=total+sm
final=total/cnt
print("Average spam confidence:",final)

如何获取文本文件中浮点数的总和？

7 个答案: